Merge pull request #627 from TomHarte/ExtraROMDetails

Extends system ROM details; provides for manual import on the Mac
2024-07-06 01:28:57 +00:00 · 2019-07-23 16:24:55 -04:00 · 2019-07-23 16:24:55 -04:00 · 90f6ca4635
commit 90f6ca4635
parent 86d709ae01 374cac0107
29 changed files with 743 additions and 132 deletions
--- a/Machines/AmstradCPC/AmstradCPC.cpp
+++ b/Machines/AmstradCPC/AmstradCPC.cpp
@ -781,27 +781,37 @@ template <bool has_fdc> class ConcreteMachine:
 			ay_.ay().set_port_handler(&key_state_);

 			// construct the list of necessary ROMs
-			std::vector<std::string> required_roms = {"amsdos.rom"};
+			const std::string machine_name = "AmstradCPC";
+			std::vector<ROMMachine::ROM> required_roms = {
+				ROMMachine::ROM(machine_name, "the Amstrad Disk Operating System", "amsdos.rom", 16*1024, 0x1fe22ecd)
+			};
 			std::string model_number;
+			uint32_t crcs[2];
 			switch(target.model) {
 				default:
 					model_number = "6128";
 					has_128k_ = true;
+					crcs[0] = 0x0219bb74;
+					crcs[1] = 0xca6af63d;
 				break;
 				case Analyser::Static::AmstradCPC::Target::Model::CPC464:
 					model_number = "464";
 					has_128k_ = false;
+					crcs[0] = 0x815752df;
+					crcs[1] = 0x7d9a3bac;
 				break;
 				case Analyser::Static::AmstradCPC::Target::Model::CPC664:
 					model_number = "664";
 					has_128k_ = false;
+					crcs[0] = 0x3f5a6dc4;
+					crcs[1] = 0x32fee492;
 				break;
 			}
-			required_roms.push_back("os" + model_number + ".rom");
-			required_roms.push_back("basic" + model_number + ".rom");
+			required_roms.emplace_back(machine_name, "the CPC " + model_number + " firmware", "os" + model_number + ".rom", 16*1024, crcs[0]);
+			required_roms.emplace_back(machine_name, "the CPC " + model_number + " BASIC ROM", "basic" + model_number + ".rom", 16*1024, crcs[1]);

 			// fetch and verify the ROMs
-			const auto roms = rom_fetcher("AmstradCPC", required_roms);
+			const auto roms = rom_fetcher(required_roms);

 			for(std::size_t index = 0; index < roms.size(); ++index) {
 				auto &data = roms[index];
--- a/Machines/Apple/AppleII/AppleII.cpp
+++ b/Machines/Apple/AppleII/AppleII.cpp
@ -347,30 +347,39 @@ template <Analyser::Static::AppleII::Target::Model model> class ConcreteMachine:

 			// Pick the required ROMs.
 			using Target = Analyser::Static::AppleII::Target;
-			std::vector<std::string> rom_names;
+			const std::string machine_name = "AppleII";
+			std::vector<ROMMachine::ROM> rom_descriptions;
 			size_t rom_size = 12*1024;
 			switch(target.model) {
 				default:
-					rom_names.push_back("apple2-character.rom");
-					rom_names.push_back("apple2o.rom");
+					rom_descriptions.emplace_back(machine_name, "the basic Apple II character ROM", "apple2-character.rom", 2*1024, 0x64f415c6);
+					rom_descriptions.emplace_back(machine_name, "the original Apple II ROM", "apple2o.rom", 12*1024, 0xba210588);
 				break;
 				case Target::Model::IIplus:
-					rom_names.push_back("apple2-character.rom");
-					rom_names.push_back("apple2.rom");
+					rom_descriptions.emplace_back(machine_name, "the basic Apple II character ROM", "apple2-character.rom", 2*1024, 0x64f415c6);
+					rom_descriptions.emplace_back(machine_name, "the Apple II+ ROM", "apple2.rom", 12*1024, 0xf66f9c26);
 				break;
 				case Target::Model::IIe:
 					rom_size += 3840;
-					rom_names.push_back("apple2eu-character.rom");
-					rom_names.push_back("apple2eu.rom");
+					rom_descriptions.emplace_back(machine_name, "the Apple IIe character ROM", "apple2eu-character.rom", 4*1024, 0x816a86f1);
+					rom_descriptions.emplace_back(machine_name, "the Apple IIe ROM", "apple2eu.rom", 32*1024, 0xe12be18d);
 				break;
 				case Target::Model::EnhancedIIe:
 					rom_size += 3840;
-					rom_names.push_back("apple2e-character.rom");
-					rom_names.push_back("apple2e.rom");
+					rom_descriptions.emplace_back(machine_name, "the Enhanced Apple IIe character ROM", "apple2e-character.rom", 4*1024, 0x2651014d);
+					rom_descriptions.emplace_back(machine_name, "the Enhanced Apple IIe ROM", "apple2e.rom", 32*1024, 0x65989942);
 				break;
 			}
-			const auto roms = rom_fetcher("AppleII", rom_names);
+			const auto roms = rom_fetcher(rom_descriptions);

+			// Try to install a Disk II card now, before checking the ROM list,
+			// to make sure that Disk II dependencies have been communicated.
+			if(target.disk_controller != Target::DiskController::None) {
+				// Apple recommended slot 6 for the (first) Disk II.
+				install_card(6, new Apple::II::DiskIICard(rom_fetcher, target.disk_controller == Target::DiskController::SixteenSector));
+			}
+
+			// Now, check and move the ROMs.
 			if(!roms[0] || !roms[1]) {
 				throw ROMMachine::Error::MissingROMs;
 			}
@ -382,11 +391,6 @@ template <Analyser::Static::AppleII::Target::Model model> class ConcreteMachine:

 			video_.set_character_rom(*roms[0]);

-			if(target.disk_controller != Target::DiskController::None) {
-				// Apple recommended slot 6 for the (first) Disk II.
-				install_card(6, new Apple::II::DiskIICard(rom_fetcher, target.disk_controller == Target::DiskController::SixteenSector));
-			}
-
 			// Set up the default memory blocks. On a II or II+ these values will never change.
 			// On a IIe they'll be affected by selection of auxiliary RAM.
 			set_main_paging();
--- a/Machines/Apple/AppleII/DiskIICard.cpp
+++ b/Machines/Apple/AppleII/DiskIICard.cpp
@ -11,12 +11,22 @@
 using namespace Apple::II;

 DiskIICard::DiskIICard(const ROMMachine::ROMFetcher &rom_fetcher, bool is_16_sector) : diskii_(2045454) {
-	const auto roms = rom_fetcher(
-		"DiskII",
-		{
-			is_16_sector ? "boot-16.rom" : "boot-13.rom",
-			is_16_sector ? "state-machine-16.rom" : "state-machine-13.rom"
+	std::vector<std::unique_ptr<std::vector<uint8_t>>> roms;
+	if(is_16_sector) {
+		roms = rom_fetcher({
+			{"DiskII", "the Disk II 16-sector boot ROM", "boot-16.rom", 256, 0xce7144f6},
+			{"DiskII", "the Disk II 16-sector state machine ROM", "state-machine-16.rom", 256, { 0x9796a238, 0xb72a2c70 } }
 		});
+	} else {
+		roms = rom_fetcher({
+			{"DiskII", "the Disk II 13-sector boot ROM", "boot-13.rom", 256, 0xd34eb2ff},
+			{"DiskII", "the Disk II 13-sector state machine ROM", "state-machine-13.rom", 256, 0x62e22620 }
+		});
+	}
+	if(!roms[0] || !roms[1]) {
+		throw ROMMachine::Error::MissingROMs;
+	}
+
 	boot_ = std::move(*roms[0]);
 	diskii_.set_state_machine(*roms[1]);
 	set_select_constraints(None);
--- a/Machines/Apple/Macintosh/Macintosh.cpp
+++ b/Machines/Apple/Macintosh/Macintosh.cpp
@ -70,33 +70,35 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
 			// Select a ROM name and determine the proper ROM and RAM sizes
 			// based on the machine model.
 			using Model = Analyser::Static::Macintosh::Target::Model;
-			std::string rom_name;
+			const std::string machine_name = "Macintosh";
 			uint32_t ram_size, rom_size;
+			std::vector<ROMMachine::ROM> rom_descriptions;
 			switch(model) {
 				default:
 				case Model::Mac128k:
 					ram_size = 128*1024;
 					rom_size = 64*1024;
-					rom_name = "mac128k.rom";
+					rom_descriptions.emplace_back(machine_name, "the Macintosh 128k ROM", "mac128k.rom", 64*1024, 0x6d0c8a28);
 				break;
 				case Model::Mac512k:
 					ram_size = 512*1024;
 					rom_size = 64*1024;
-					rom_name = "mac512k.rom";
+					rom_descriptions.emplace_back(machine_name, "the Macintosh 512k ROM", "mac512k.rom", 64*1024, 0xcf759e0d);
 				break;
 				case Model::Mac512ke:
-				case Model::MacPlus:
+				case Model::MacPlus: {
 					ram_size = 512*1024;
 					rom_size = 128*1024;
-					rom_name = "macplus.rom";
-				break;
+					const std::initializer_list<uint32_t> crc32s = { 0x4fa5b399, 0x7cacd18f, 0xb2102e8e };
+					rom_descriptions.emplace_back(machine_name, "the Macintosh Plus ROM", "macplus.rom", 128*1024, crc32s);
+				} break;
 			}
 			ram_mask_ = (ram_size >> 1) - 1;
 			rom_mask_ = (rom_size >> 1) - 1;
 			video_.set_ram_mask(ram_mask_);

 			// Grab a copy of the ROM and convert it into big-endian data.
-			const auto roms = rom_fetcher("Macintosh", { rom_name });
+			const auto roms = rom_fetcher(rom_descriptions);
 			if(!roms[0]) {
 				throw ROMMachine::Error::MissingROMs;
 			}
--- a/Machines/ColecoVision/ColecoVision.cpp
+++ b/Machines/ColecoVision/ColecoVision.cpp
@ -131,8 +131,7 @@ class ConcreteMachine:
 			joysticks_.emplace_back(new Joystick);

 			const auto roms = rom_fetcher(
-				"ColecoVision",
-				{ "coleco.rom" });
+				{ {"ColecoVision", "the ColecoVision BIOS", "coleco.rom", 8*1024, 0x3aa93ef3} });

 			if(!roms[0]) {
 				throw ROMMachine::Error::MissingROMs;
--- a/Machines/Commodore/1540/Implementation/C1540.cpp
+++ b/Machines/Commodore/1540/Implementation/C1540.cpp
@ -39,13 +39,20 @@ MachineBase::MachineBase(Personality personality, const ROMMachine::ROMFetcher &
 	// attach the only drive there is
 	set_drive(drive_);

-	std::string rom_name;
+	std::string device_name;
+	uint32_t crc = 0;
 	switch(personality) {
-		case Personality::C1540:	rom_name = "1540.bin";	break;
-		case Personality::C1541:	rom_name = "1541.bin";	break;
+		case Personality::C1540:
+			device_name = "1540";
+			crc = 0x718d42b1;
+		break;
+		case Personality::C1541:
+			device_name = "1541";
+			crc = 0xfb760019;
+		break;
 	}

-	auto roms = rom_fetcher("Commodore1540", {rom_name});
+	auto roms = rom_fetcher({ {"Commodore1540", "the " + device_name + " ROM", device_name + ".bin", 16*1024, crc} });
 	if(!roms[0]) {
 		throw ROMMachine::Error::MissingROMs;
 	}
--- a/Machines/Commodore/Vic-20/Vic20.cpp
+++ b/Machines/Commodore/Vic-20/Vic20.cpp
@ -323,31 +323,34 @@ class ConcreteMachine:
 			// install a joystick
 			joysticks_.emplace_back(new Joystick(*user_port_via_port_handler_, *keyboard_via_port_handler_));

-			std::vector<std::string> rom_names = { "basic.bin" };
+			const std::string machine_name = "Vic20";
+			std::vector<ROMMachine::ROM> rom_names = {
+				{machine_name, "the VIC-20 BASIC ROM", "basic.bin", 8*1024, 0xdb4c43c1}
+			};
 			switch(target.region) {
 				default:
-					rom_names.push_back("characters-english.bin");
-					rom_names.push_back("kernel-pal.bin");
+					rom_names.emplace_back(machine_name, "the English-language VIC-20 character ROM", "characters-english.bin", 4*1024, 0x83e032a6);
+					rom_names.emplace_back(machine_name, "the English-language PAL VIC-20 kernel ROM", "kernel-pal.bin", 8*1024, 0x4be07cb4);
 				break;
 				case Analyser::Static::Commodore::Target::Region::American:
-					rom_names.push_back("characters-english.bin");
-					rom_names.push_back("kernel-ntsc.bin");
+					rom_names.emplace_back(machine_name, "the English-language VIC-20 character ROM", "characters-english.bin", 4*1024, 0x83e032a6);
+					rom_names.emplace_back(machine_name, "the English-language NTSC VIC-20 kernel ROM", "kernel-ntsc.bin", 8*1024, 0xe5e7c174);
 				break;
 				case Analyser::Static::Commodore::Target::Region::Danish:
-					rom_names.push_back("characters-danish.bin");
-					rom_names.push_back("kernel-danish.bin");
+					rom_names.emplace_back(machine_name, "the Danish VIC-20 character ROM", "characters-danish.bin", 4*1024, 0x7fc11454);
+					rom_names.emplace_back(machine_name, "the Danish VIC-20 kernel ROM", "kernel-danish.bin", 8*1024, 0x02adaf16);
 				break;
 				case Analyser::Static::Commodore::Target::Region::Japanese:
-					rom_names.push_back("characters-japanese.bin");
-					rom_names.push_back("kernel-japanese.bin");
+					rom_names.emplace_back(machine_name, "the Japanese VIC-20 character ROM", "characters-japanese.bin", 4*1024, 0xfcfd8a4b);
+					rom_names.emplace_back(machine_name, "the Japanese VIC-20 kernel ROM", "kernel-japanese.bin", 8*1024, 0x336900d7);
 				break;
 				case Analyser::Static::Commodore::Target::Region::Swedish:
-					rom_names.push_back("characters-swedish.bin");
-					rom_names.push_back("kernel-japanese.bin");
+					rom_names.emplace_back(machine_name, "the Swedish VIC-20 character ROM", "characters-swedish.bin", 4*1024, 0xd808551d);
+					rom_names.emplace_back(machine_name, "the Swedish VIC-20 kernel ROM", "kernel-swedish.bin", 8*1024, 0xb2a60662);
 				break;
 			}

-			const auto roms = rom_fetcher("Vic20", rom_names);
+			const auto roms = rom_fetcher(rom_names);

 			for(const auto &rom: roms) {
 				if(!rom) {
--- a/Machines/Electron/Electron.cpp
+++ b/Machines/Electron/Electron.cpp
@ -64,16 +64,20 @@ class ConcreteMachine:
 			speaker_.set_input_rate(2000000 / SoundGenerator::clock_rate_divider);
 			speaker_.set_high_frequency_cutoff(7000);

-			std::vector<std::string> rom_names = {"basic.rom", "os.rom"};
+			const std::string machine_name = "Electron";
+			std::vector<ROMMachine::ROM> required_roms = {
+				{machine_name, "the Acorn BASIC II ROM", "basic.rom", 16*1024, 0x79434781},
+				{machine_name, "the Electron MOS ROM", "os.rom", 16*1024, 0xbf63fb1f}
+			};
 			if(target.has_adfs) {
-				rom_names.push_back("ADFS-E00_1.rom");
-				rom_names.push_back("ADFS-E00_2.rom");
+				required_roms.emplace_back(machine_name, "the E00 ADFS ROM, first slot", "ADFS-E00_1.rom", 16*1024, 0x51523993);
+				required_roms.emplace_back(machine_name, "the E00 ADFS ROM, second slot", "ADFS-E00_2.rom", 16*1024, 0x8d17de0e);
 			}
-			const size_t dfs_rom_position = rom_names.size();
+			const size_t dfs_rom_position = required_roms.size();
 			if(target.has_dfs) {
-				rom_names.push_back("DFS-1770-2.20.rom");
+				required_roms.emplace_back(machine_name, "the 1770 DFS ROM", "DFS-1770-2.20.rom", 16*1024, 0xf3dc9bc5);
 			}
-			const auto roms = rom_fetcher("Electron", rom_names);
+			const auto roms = rom_fetcher(required_roms);

 			for(const auto &rom: roms) {
 				if(!rom) {
--- a/Machines/MSX/MSX.cpp
+++ b/Machines/MSX/MSX.cpp
@ -173,16 +173,20 @@ class ConcreteMachine:
 			mixer_.set_relative_volumes({0.5f, 0.1f, 0.4f});

 			// Install the proper TV standard and select an ideal BIOS name.
-			std::vector<std::string> rom_names = {"msx.rom"};
+			const std::string machine_name = "MSX";
+			std::vector<ROMMachine::ROM> required_roms = {
+				{machine_name, "any MSX BIOS", "msx.rom", 32*1024, 0x94ee12f3}
+			};

 			bool is_ntsc = true;
 			uint8_t character_generator = 1;	/* 0 = Japan, 1 = USA, etc, 2 = USSR */
 			uint8_t date_format = 1;			/* 0 = Y/M/D, 1 = M/D/Y, 2 = D/M/Y */
 			uint8_t keyboard = 1;				/* 0 = Japan, 1 = USA, 2 = France, 3 = UK, 4 = Germany, 5 = USSR, 6 = Spain */

+			// TODO: CRCs below are incomplete, at best.
 			switch(target.region) {
 				case Target::Region::Japan:
-					rom_names.push_back("msx-japanese.rom");
+					required_roms.emplace_back(machine_name, "a Japanese MSX BIOS", "msx-japanese.rom", 32*1024, 0xee229390);
 					vdp_.set_tv_standard(TI::TMS::TVStandard::NTSC);

 					is_ntsc = true;
@ -190,7 +194,7 @@ class ConcreteMachine:
 					date_format = 0;
 				break;
 				case Target::Region::USA:
-					rom_names.push_back("msx-american.rom");
+					required_roms.emplace_back(machine_name, "an American MSX BIOS", "msx-american.rom", 32*1024, 0);
 					vdp_.set_tv_standard(TI::TMS::TVStandard::NTSC);

 					is_ntsc = true;
@ -198,7 +202,7 @@ class ConcreteMachine:
 					date_format = 1;
 				break;
 				case Target::Region::Europe:
-					rom_names.push_back("msx-european.rom");
+					required_roms.emplace_back(machine_name, "a European MSX BIOS", "msx-european.rom", 32*1024, 0);
 					vdp_.set_tv_standard(TI::TMS::TVStandard::PAL);

 					is_ntsc = false;
@ -211,10 +215,10 @@ class ConcreteMachine:
 			// but failing that fall back on patching the main one.
 			size_t disk_index = 0;
 			if(target.has_disk_drive) {
-				disk_index = rom_names.size();
-				rom_names.push_back("disk.rom");
+				disk_index = required_roms.size();
+				required_roms.emplace_back(machine_name, "the MSX-DOS ROM", "disk.rom", 16*1024, 0x721f61df);
 			}
-			const auto roms = rom_fetcher("MSX", rom_names);
+			const auto roms = rom_fetcher(required_roms);

 			if((!roms[0] && !roms[1]) || (target.has_disk_drive && !roms[2])) {
 				throw ROMMachine::Error::MissingROMs;
--- a/Machines/MasterSystem/MasterSystem.cpp
+++ b/Machines/MasterSystem/MasterSystem.cpp
@ -132,7 +132,12 @@ class ConcreteMachine:

 			// Load the BIOS if relevant.
 			if(has_bios()) {
-				const auto roms = rom_fetcher("MasterSystem", {"bios.sms"});
+				// TODO: there's probably a million other versions of the Master System BIOS; try to build a
+				// CRC32 catalogue of those. So far:
+				//
+				//	0072ed54 = US/European BIOS 1.3
+				//	48d44a13 = Japanese BIOS 2.1
+				const auto roms = rom_fetcher({ {"MasterSystem", "the Master System BIOS", "bios.sms", 8*1024, { 0x0072ed54, 0x48d44a13 } } });
 				if(!roms[0]) {
 					// No BIOS found; attempt to boot as though it has already disabled itself.
 					memory_control_ |= 0x08;
--- a/Machines/Oric/Oric.cpp
+++ b/Machines/Oric/Oric.cpp
@ -228,19 +228,34 @@ template <Analyser::Static::Oric::Target::DiskInterface disk_interface> class Co
 				diskii_.set_clocking_hint_observer(this);
 			}

-			std::vector<std::string> rom_names = {"colour.rom"};
+			const std::string machine_name = "Oric";
+			std::vector<ROMMachine::ROM> rom_names = { {machine_name, "the Oric colour ROM", "colour.rom", 128, 0xd50fca65} };
 			switch(target.rom) {
-				case Analyser::Static::Oric::Target::ROM::BASIC10: rom_names.push_back("basic10.rom");	break;
-				case Analyser::Static::Oric::Target::ROM::BASIC11: rom_names.push_back("basic11.rom");	break;
-				case Analyser::Static::Oric::Target::ROM::Pravetz: rom_names.push_back("pravetz.rom");	break;
+				case Analyser::Static::Oric::Target::ROM::BASIC10:
+					rom_names.emplace_back(machine_name, "Oric BASIC 1.0", "basic10.rom", 16*1024, 0xf18710b4);
+				break;
+				case Analyser::Static::Oric::Target::ROM::BASIC11:
+					rom_names.emplace_back(machine_name, "Oric BASIC 1.1", "basic11.rom", 16*1024, 0xc3a92bef);
+				break;
+				case Analyser::Static::Oric::Target::ROM::Pravetz:
+					rom_names.emplace_back(machine_name, "Pravetz BASIC", "pravetz.rom", 16*1024, 0x58079502);
+				break;
 			}
+			size_t diskii_state_machine_index = 0;
 			switch(disk_interface) {
 				default: break;
-				case Analyser::Static::Oric::Target::DiskInterface::Microdisc:	rom_names.push_back("microdisc.rom");	break;
-				case Analyser::Static::Oric::Target::DiskInterface::Pravetz:	rom_names.push_back("8dos.rom");		break;
+				case Analyser::Static::Oric::Target::DiskInterface::Microdisc:
+					rom_names.emplace_back(machine_name, "the ORIC Microdisc ROM", "microdisc.rom", 8*1024, 0xa9664a9c);
+				break;
+				case Analyser::Static::Oric::Target::DiskInterface::Pravetz:
+					rom_names.emplace_back(machine_name, "the 8DOS boot ROM", "8dos.rom", 512, 0x49a74c06);
+					// These ROM details are coupled with those in the DiskIICard.
+					diskii_state_machine_index = rom_names.size();
+					rom_names.push_back({"DiskII", "the Disk II 16-sector state machine ROM", "state-machine-16.rom", 256, { 0x9796a238, 0xb72a2c70 }});
+				break;
 			}

-			const auto roms = rom_fetcher("Oric", rom_names);
+			const auto roms = rom_fetcher(rom_names);

 			for(std::size_t index = 0; index < roms.size(); ++index) {
 				if(!roms[index]) {
@ -261,11 +276,7 @@ template <Analyser::Static::Oric::Target::DiskInterface disk_interface> class Co
 					pravetz_rom_ = std::move(*roms[2]);
 					pravetz_rom_.resize(512);

-					auto state_machine_rom = rom_fetcher("DiskII", {"state-machine-16.rom"});
-					if(!state_machine_rom[0]) {
-						throw ROMMachine::Error::MissingROMs;
-					}
-					diskii_.set_state_machine(*state_machine_rom[0]);
+					diskii_.set_state_machine(*roms[diskii_state_machine_index]);
 				} break;
 			}

--- a/Machines/ROMMachine.hpp
+++ b/Machines/ROMMachine.hpp
@ -16,15 +16,41 @@

 namespace ROMMachine {

+/*!
+	Describes a ROM image; this term is used in this emulator strictly in the sense of firmware —
+	system software that is an inherent part of a machine.
+*/
+struct ROM {
+	/// The machine with which this ROM is associated, in a form that is safe for using as
+	/// part of a file name.
+	std::string machine_name;
+	/// A descriptive name for this ROM, suitable for use in a bullet-point list, a bracket
+	/// clause, etc, e.g. "the Electron MOS 1.0".
+	std::string descriptive_name;
+	/// An idiomatic file name for this ROM, e.g. "os10.rom".
+	std::string file_name;
+	/// The expected size of this ROM in bytes, e.g. 32768.
+	size_t size = 0;
+	/// CRC32s for all known acceptable copies of this ROM; intended to allow a host platform
+	/// to test user-provided ROMs of unknown provenance. **Not** intended to be used
+	/// to exclude ROMs where the user's intent is otherwise clear.
+	std::vector<uint32_t> crc32s;
+
+	ROM(std::string machine_name, std::string descriptive_name, std::string file_name, size_t size, uint32_t crc32) :
+		machine_name(machine_name), descriptive_name(descriptive_name), file_name(file_name), size(size), crc32s({crc32}) {}
+	ROM(std::string machine_name, std::string descriptive_name, std::string file_name, size_t size, std::initializer_list<uint32_t> crc32s) :
+		machine_name(machine_name), descriptive_name(descriptive_name), file_name(file_name), size(size), crc32s(crc32s) {}
+};
+
 /*!
 	Defines the signature for a function that must be supplied by the host environment in order to give machines
 	a route for fetching any system ROMs they might need.

-	The caller will supply the idiomatic name of the machine plus a vector of the names of ROM files that it expects
-	to be present. The recevier should return a vector of unique_ptrs that either contain the contents of the
-	ROM from @c names that corresponds by index, or else are the nullptr
+	The caller will supply a vector of the names of ROM files that it would like to inspect. The recevier should
+	return a vector of unique_ptrs that either contain the contents of the ROM from @c names that corresponds by
+	index, or else are @c nullptr.
 */
-typedef std::function<std::vector<std::unique_ptr<std::vector<uint8_t>>>(const std::string &machine, const std::vector<std::string> &names)> ROMFetcher;
+typedef std::function<std::vector<std::unique_ptr<std::vector<uint8_t>>>(const std::vector<ROM> &roms)> ROMFetcher;

 enum class Error {
 	MissingROMs
--- a/Machines/ZX8081/ZX8081.cpp
+++ b/Machines/ZX8081/ZX8081.cpp
@ -76,7 +76,11 @@ template<bool is_zx81> class ConcreteMachine:
 			clear_all_keys();

 			const bool use_zx81_rom = target.is_ZX81 || target.ZX80_uses_ZX81_ROM;
-			const auto roms = rom_fetcher("ZX8081", { use_zx81_rom ? "zx81.rom" : "zx80.rom" });
+			const auto roms =
+				use_zx81_rom ?
+					rom_fetcher({ {"ZX8081", "the ZX81 BASIC ROM", "zx81.rom", 8 * 1024, 0x4b1dd6eb} }) :
+					rom_fetcher({ {"ZX8081", "the ZX80 BASIC ROM", "zx80.rom", 4 * 1024, 0x4c7fc597} });
+
 			if(!roms[0]) throw ROMMachine::Error::MissingROMs;

 			rom_ = std::move(*roms[0]);
--- a/Signal.xcodeproj/project.pbxproj
+++ b/Signal.xcodeproj/project.pbxproj
@ -145,7 +145,6 @@
 		4B1EDB451E39A0AC009D6819 /* chip.png in Resources */ = {isa = PBXBuildFile; fileRef = 4B1EDB431E39A0AC009D6819 /* chip.png */; };
 		4B2A332D1DB86821002876E3 /* OricOptions.xib in Resources */ = {isa = PBXBuildFile; fileRef = 4B2A332B1DB86821002876E3 /* OricOptions.xib */; };
 		4B2A539F1D117D36003C6002 /* CSAudioQueue.m in Sources */ = {isa = PBXBuildFile; fileRef = 4B2A53911D117D36003C6002 /* CSAudioQueue.m */; };
-		4B2A53A01D117D36003C6002 /* CSMachine.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B2A53961D117D36003C6002 /* CSMachine.mm */; };
 		4B2B3A4B1F9B8FA70062DABF /* Typer.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B2B3A471F9B8FA70062DABF /* Typer.cpp */; };
 		4B2B3A4C1F9B8FA70062DABF /* MemoryFuzzer.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B2B3A481F9B8FA70062DABF /* MemoryFuzzer.cpp */; };
 		4B2BFC5F1D613E0200BA3AA9 /* TapePRG.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B2BFC5D1D613E0200BA3AA9 /* TapePRG.cpp */; };
@ -633,7 +632,6 @@
 		4BC76E691C98E31700E6EF73 /* FIRFilter.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC76E671C98E31700E6EF73 /* FIRFilter.cpp */; };
 		4BC76E6B1C98F43700E6EF73 /* Accelerate.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 4BC76E6A1C98F43700E6EF73 /* Accelerate.framework */; };
 		4BC91B831D1F160E00884B76 /* CommodoreTAP.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC91B811D1F160E00884B76 /* CommodoreTAP.cpp */; };
-		4BC9DF451D044FCA00F44158 /* ROMImages in Resources */ = {isa = PBXBuildFile; fileRef = 4BC9DF441D044FCA00F44158 /* ROMImages */; };
 		4BC9DF4F1D04691600F44158 /* 6560.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC9DF4D1D04691600F44158 /* 6560.cpp */; };
 		4BC9E1EE1D23449A003FCEE4 /* 6502InterruptTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4BC9E1ED1D23449A003FCEE4 /* 6502InterruptTests.swift */; };
 		4BCA6CC81D9DD9F000C2D7B2 /* CommodoreROM.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BCA6CC61D9DD9F000C2D7B2 /* CommodoreROM.cpp */; };
@ -666,6 +664,11 @@
 		4BD67DCC209BE4D700AB2146 /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BD67DCA209BE4D600AB2146 /* StaticAnalyser.cpp */; };
 		4BD67DD0209BF27B00AB2146 /* Encoder.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BD67DCE209BF27B00AB2146 /* Encoder.cpp */; };
 		4BD67DD1209BF27B00AB2146 /* Encoder.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BD67DCE209BF27B00AB2146 /* Encoder.cpp */; };
+		4BDA00DA22E60EE300AC3CD0 /* ROMRequester.xib in Resources */ = {isa = PBXBuildFile; fileRef = 4BDA00D922E60EE300AC3CD0 /* ROMRequester.xib */; };
+		4BDA00DD22E622C200AC3CD0 /* ROMImages in Resources */ = {isa = PBXBuildFile; fileRef = 4BC9DF441D044FCA00F44158 /* ROMImages */; };
+		4BDA00E022E644AF00AC3CD0 /* CSROMReceiverView.m in Sources */ = {isa = PBXBuildFile; fileRef = 4BDA00DF22E644AF00AC3CD0 /* CSROMReceiverView.m */; };
+		4BDA00E422E663B900AC3CD0 /* NSData+CRC32.m in Sources */ = {isa = PBXBuildFile; fileRef = 4BDA00E222E663B900AC3CD0 /* NSData+CRC32.m */; };
+		4BDA00E622E699B000AC3CD0 /* CSMachine.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B2A53961D117D36003C6002 /* CSMachine.mm */; };
 		4BDB61EB2032806E0048AF91 /* CSAtari2600.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B2A539A1D117D36003C6002 /* CSAtari2600.mm */; };
 		4BDB61EC203285AE0048AF91 /* Atari2600OptionsPanel.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B8FE21F1DA19D7C0090D3CE /* Atari2600OptionsPanel.swift */; };
 		4BDDBA991EF3451200347E61 /* Z80MachineCycleTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4BDDBA981EF3451200347E61 /* Z80MachineCycleTests.swift */; };
@ -1473,6 +1476,11 @@
 		4BD67DCE209BF27B00AB2146 /* Encoder.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = Encoder.cpp; sourceTree = "<group>"; };
 		4BD67DCF209BF27B00AB2146 /* Encoder.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Encoder.hpp; sourceTree = "<group>"; };
 		4BD9137D1F311BC5009BCF85 /* i8255.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = i8255.hpp; path = 8255/i8255.hpp; sourceTree = "<group>"; };
+		4BDA00D922E60EE300AC3CD0 /* ROMRequester.xib */ = {isa = PBXFileReference; lastKnownFileType = file.xib; path = ROMRequester.xib; sourceTree = "<group>"; };
+		4BDA00DE22E644AF00AC3CD0 /* CSROMReceiverView.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = CSROMReceiverView.h; sourceTree = "<group>"; };
+		4BDA00DF22E644AF00AC3CD0 /* CSROMReceiverView.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = CSROMReceiverView.m; sourceTree = "<group>"; };
+		4BDA00E222E663B900AC3CD0 /* NSData+CRC32.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "NSData+CRC32.m"; sourceTree = "<group>"; };
+		4BDA00E322E663B900AC3CD0 /* NSData+CRC32.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSData+CRC32.h"; sourceTree = "<group>"; };
 		4BDB3D8522833321002D3CEE /* Keyboard.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Keyboard.hpp; sourceTree = "<group>"; };
 		4BDCC5F81FB27A5E001220C5 /* ROMMachine.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = ROMMachine.hpp; sourceTree = "<group>"; };
 		4BDDBA981EF3451200347E61 /* Z80MachineCycleTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Z80MachineCycleTests.swift; sourceTree = "<group>"; };
@ -1736,13 +1744,15 @@
 				4BBC34241D2208B100FFC9DF /* CSFastLoading.h */,
 				4B2A53951D117D36003C6002 /* CSMachine.h */,
 				4B643F3C1D77AE5C00D431D6 /* CSMachine+Target.h */,
-				4B98A05C1FFAD3F600ADF63B /* CSROMFetcher.hpp */,
 				4B2A53971D117D36003C6002 /* KeyCodes.h */,
 				4B8FE2251DA1DE2D0090D3CE /* NSBundle+DataResource.h */,
+				4BDA00E322E663B900AC3CD0 /* NSData+CRC32.h */,
 				4BA61EAE1D91515900B3C876 /* NSData+StdVector.h */,
-				4B98A05D1FFAD3F600ADF63B /* CSROMFetcher.mm */,
+				4B98A05C1FFAD3F600ADF63B /* CSROMFetcher.hpp */,
 				4B8FE2261DA1DE2D0090D3CE /* NSBundle+DataResource.m */,
+				4BDA00E222E663B900AC3CD0 /* NSData+CRC32.m */,
 				4B2A53961D117D36003C6002 /* CSMachine.mm */,
+				4B98A05D1FFAD3F600ADF63B /* CSROMFetcher.mm */,
 				4BA61EAF1D91515900B3C876 /* NSData+StdVector.mm */,
 				4B643F3B1D77AD6D00D431D6 /* StaticAnalyser */,
 				4B2A53981D117D36003C6002 /* Wrappers */,
@ -2944,6 +2954,7 @@
 				4BE5F85A1C3E1C2500C43F01 /* Resources */,
 				4BD5F1961D1352A000631CD1 /* Updater */,
 				4B55CE5A1C3B7D6F0093A61B /* Views */,
+				4BDA00DB22E60EE900AC3CD0 /* ROMRequester */,
 			);
 			path = "Clock Signal";
 			sourceTree = "<group>";
@ -3297,6 +3308,16 @@
 			name = 8255;
 			sourceTree = "<group>";
 		};
+		4BDA00DB22E60EE900AC3CD0 /* ROMRequester */ = {
+			isa = PBXGroup;
+			children = (
+				4BDA00D922E60EE300AC3CD0 /* ROMRequester.xib */,
+				4BDA00DE22E644AF00AC3CD0 /* CSROMReceiverView.h */,
+				4BDA00DF22E644AF00AC3CD0 /* CSROMReceiverView.m */,
+			);
+			path = ROMRequester;
+			sourceTree = "<group>";
+		};
 		4BE5F85A1C3E1C2500C43F01 /* Resources */ = {
 			isa = PBXGroup;
 			children = (
@ -3544,6 +3565,7 @@
 				4BB73EA91B587A5100552FC2 /* Assets.xcassets in Resources */,
 				4B79E4451E3AF38600141F11 /* floppy35.png in Resources */,
 				4B55DD8420DF06680043F2E5 /* MachinePicker.xib in Resources */,
+				4BDA00DA22E60EE300AC3CD0 /* ROMRequester.xib in Resources */,
 				4BC5FC3020CDDDEF00410AA0 /* AppleIIOptions.xib in Resources */,
 				4B1EDB451E39A0AC009D6819 /* chip.png in Resources */,
 				4B2A332D1DB86821002876E3 /* OricOptions.xib in Resources */,
@ -3555,7 +3577,6 @@
 				4BB73EAC1B587A5100552FC2 /* MainMenu.xib in Resources */,
 				4B8FE21D1DA19D5F0090D3CE /* QuickLoadCompositeOptions.xib in Resources */,
 				4B79E4461E3AF38600141F11 /* floppy525.png in Resources */,
-				4BC9DF451D044FCA00F44158 /* ROMImages in Resources */,
 				4BEEE6BD20DC72EB003723BF /* CompositeOptions.xib in Resources */,
 				4B1497981EE4B97F00CE2596 /* ZX8081Options.xib in Resources */,
 			);
@ -3610,6 +3631,7 @@
 				4BB299B91B587D8400A49093 /* rorz in Resources */,
 				4BB299F61B587D8400A49093 /* tsxn in Resources */,
 				4BB298F11B587D8400A49093 /*  start in Resources */,
+				4BDA00DD22E622C200AC3CD0 /* ROMImages in Resources */,
 				4BB299061B587D8400A49093 /* asla in Resources */,
 				4BB299901B587D8400A49093 /* lsrn in Resources */,
 				4BB298FE1B587D8400A49093 /* anday in Resources */,
@ -4067,6 +4089,7 @@
 				4B595FAD2086DFBA0083CAA8 /* AudioToggle.cpp in Sources */,
 				4B1497921EE4B5A800CE2596 /* ZX8081.cpp in Sources */,
 				4B643F3F1D77B88000D431D6 /* DocumentController.swift in Sources */,
+				4BDA00E422E663B900AC3CD0 /* NSData+CRC32.m in Sources */,
 				4BB4BFB022A42F290069048D /* MacintoshIMG.cpp in Sources */,
 				4B05401E219D1618001BF69C /* ScanTarget.cpp in Sources */,
 				4B4518861F75E91A00926311 /* MFMDiskController.cpp in Sources */,
@ -4099,6 +4122,7 @@
 				4B55CE5F1C3B7D960093A61B /* MachineDocument.swift in Sources */,
 				4B2B3A4C1F9B8FA70062DABF /* MemoryFuzzer.cpp in Sources */,
 				4B7913CC1DFCD80E00175A82 /* Video.cpp in Sources */,
+				4BDA00E622E699B000AC3CD0 /* CSMachine.mm in Sources */,
 				4B4518831F75E91A00926311 /* PCMTrack.cpp in Sources */,
 				4B45189F1F75FD1C00926311 /* AcornADF.cpp in Sources */,
 				4B7136911F789C93008B8ED9 /* SegmentParser.cpp in Sources */,
@ -4120,6 +4144,7 @@
 				4B4518851F75E91A00926311 /* DiskController.cpp in Sources */,
 				4B8334841F5DA0360097E338 /* Z80Storage.cpp in Sources */,
 				4BA61EB01D91515900B3C876 /* NSData+StdVector.mm in Sources */,
+				4BDA00E022E644AF00AC3CD0 /* CSROMReceiverView.m in Sources */,
 				4BD191F42191180E0042E144 /* ScanTarget.cpp in Sources */,
 				4BCD634922D6756400F567F1 /* MacintoshDoubleDensityDrive.cpp in Sources */,
 				4B0F94FE208C1A1600FE41D9 /* NIB.cpp in Sources */,
@ -4193,7 +4218,6 @@
 				4BF437EE209D0F7E008CBD6B /* SegmentParser.cpp in Sources */,
 				4B8334861F5DA3780097E338 /* 6502Storage.cpp in Sources */,
 				4B8FE2271DA1DE2D0090D3CE /* NSBundle+DataResource.m in Sources */,
-				4B2A53A01D117D36003C6002 /* CSMachine.mm in Sources */,
 				4BC91B831D1F160E00884B76 /* CommodoreTAP.cpp in Sources */,
 				4B55DD8320DF06680043F2E5 /* MachinePicker.swift in Sources */,
 				4B2A539F1D117D36003C6002 /* CSAudioQueue.m in Sources */,
--- a/Signal/Base.lproj/MachineDocument.xib
+++ b/Signal/Base.lproj/MachineDocument.xib
@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="14113" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="14490.70" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
    <dependencies>
        <deployment identifier="macosx"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="14113"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="14490.70"/>
        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
    </dependencies>
    <objects>
@ -14,7 +14,7 @@
        </customObject>
        <customObject id="-1" userLabel="First Responder" customClass="FirstResponder"/>
        <customObject id="-3" userLabel="Application" customClass="NSObject"/>
-        <window title="Window" allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" oneShot="NO" releasedWhenClosed="NO" showsToolbarButton="NO" visibleAtLaunch="NO" animationBehavior="default" id="xOd-HO-29H" userLabel="Window">
+        <window title="Window" allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" releasedWhenClosed="NO" visibleAtLaunch="NO" animationBehavior="default" id="xOd-HO-29H" userLabel="Window">
            <windowStyleMask key="styleMask" titled="YES" closable="YES" miniaturizable="YES" resizable="YES"/>
            <windowCollectionBehavior key="collectionBehavior" fullScreenPrimary="YES"/>
            <windowPositionMask key="initialPositionMask" leftStrut="YES" rightStrut="YES" topStrut="YES" bottomStrut="YES"/>
@ -25,7 +25,7 @@
                <rect key="frame" x="0.0" y="0.0" width="600" height="450"/>
                <autoresizingMask key="autoresizingMask"/>
                <subviews>
-                    <openGLView hidden="YES" useAuxiliaryDepthBufferStencil="NO" allowOffline="YES" wantsBestResolutionOpenGLSurface="YES" translatesAutoresizingMaskIntoConstraints="NO" id="DEG-fq-cjd" customClass="CSOpenGLView">
+                    <openGLView hidden="YES" wantsLayer="YES" useAuxiliaryDepthBufferStencil="NO" allowOffline="YES" wantsBestResolutionOpenGLSurface="YES" translatesAutoresizingMaskIntoConstraints="NO" id="DEG-fq-cjd" customClass="CSOpenGLView">
                        <rect key="frame" x="0.0" y="0.0" width="600" height="450"/>
                    </openGLView>
                </subviews>
@ -36,6 +36,11 @@
                    <constraint firstItem="DEG-fq-cjd" firstAttribute="width" secondItem="gIp-Ho-8D9" secondAttribute="width" id="mYS-bH-DST"/>
                </constraints>
            </view>
+            <userDefinedRuntimeAttributes>
+                <userDefinedRuntimeAttribute type="color" keyPath="backgroundColor">
+                    <color key="value" white="0.0" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
+                </userDefinedRuntimeAttribute>
+            </userDefinedRuntimeAttributes>
            <connections>
                <outlet property="delegate" destination="-2" id="0bl-1N-x8E"/>
                <outlet property="initialFirstResponder" destination="DEG-fq-cjd" id="9RI-Kx-QeN"/>
--- a/Signal/ClockSignal-Bridging-Header.h
+++ b/Signal/ClockSignal-Bridging-Header.h
@ -10,10 +10,13 @@

 #import "CSStaticAnalyser.h"

-#import	"CSOpenGLView.h"
 #import "CSAudioQueue.h"
+#import	"CSOpenGLView.h"
+#import "CSROMReceiverView.h"

 #import "CSBestEffortUpdater.h"
 #import "CSJoystickManager.h"

+#import "NSData+CRC32.h"
+
 #include "KeyCodes.h"
--- a/Signal/Documents/MachineDocument.swift
+++ b/Signal/Documents/MachineDocument.swift
@ -16,7 +16,8 @@ class MachineDocument:
 	CSOpenGLViewDelegate,
 	CSOpenGLViewResponderDelegate,
 	CSBestEffortUpdaterDelegate,
-	CSAudioQueueDelegate
+	CSAudioQueueDelegate,
+	CSROMReciverViewDelegate
 {
 	fileprivate let actionLock = NSLock()
 	fileprivate let drawLock = NSLock()
@ -152,12 +153,27 @@ class MachineDocument:
 	}

 	// MARK: configuring
+	fileprivate var missingROMs: [CSMissingROM] = []
+	fileprivate var selectedMachine: CSStaticAnalyser?
+
 	func configureAs(_ analysis: CSStaticAnalyser) {
-		if let machine = CSMachine(analyser: analysis) {
+		let missingROMs = NSMutableArray()
+		if let machine = CSMachine(analyser: analysis, missingROMs: missingROMs) {
+			self.selectedMachine = nil
 			self.machine = machine
 			self.optionsPanelNibName = analysis.optionsPanelNibName
 			setupMachineOutput()
 			setupActivityDisplay()
+		} else {
+			// Store the selected machine and list of missing ROMs, and
+			// show the missing ROMs dialogue.
+			self.missingROMs = []
+			for untypedMissingROM in missingROMs {
+				self.missingROMs.append(untypedMissingROM as! CSMissingROM)
+			}
+
+			self.selectedMachine = analysis
+			requestRoms()
 		}
 	}

@ -303,19 +319,173 @@ class MachineDocument:
 		}
 	}

-	// MARK: New machine creation
+	// MARK: New machine creation.
 	@IBOutlet var machinePicker: MachinePicker?
 	@IBOutlet var machinePickerPanel: NSWindow?
 	@IBAction func createMachine(_ sender: NSButton?) {
-		self.configureAs(machinePicker!.selectedMachine())
-		machinePicker = nil
+		let selectedMachine = machinePicker!.selectedMachine()
 		self.windowControllers[0].window?.endSheet(self.machinePickerPanel!)
+		machinePicker = nil
+		self.configureAs(selectedMachine)
 	}

 	@IBAction func cancelCreateMachine(_ sender: NSButton?) {
 		close()
 	}

+	// MARK: User ROM provision.
+	@IBOutlet var romRequesterPanel: NSWindow?
+	@IBOutlet var romRequesterText: NSTextField?
+	@IBOutlet var romReceiverErrorField: NSTextField?
+	@IBOutlet var romReceiverView: CSROMReceiverView?
+	private var romRequestBaseText = ""
+	func requestRoms() {
+		// Load the ROM requester dialogue.
+		Bundle.main.loadNibNamed("ROMRequester", owner: self, topLevelObjects: nil)
+		self.romReceiverView!.delegate = self
+		self.romRequestBaseText = romRequesterText!.stringValue
+		romReceiverErrorField?.alphaValue = 0.0
+
+		// Populate the current absentee list.
+		populateMissingRomList()
+
+		// Show the thing.
+		self.windowControllers[0].window?.beginSheet(self.romRequesterPanel!, completionHandler: nil)
+	}
+
+	@IBAction func cancelRequestROMs(_ sender: NSButton?) {
+		close()
+	}
+
+	func populateMissingRomList() {
+		// Fill in the missing details; first build a list of all the individual
+		// line items.
+		var requestLines: [String] = []
+		for missingROM in self.missingROMs {
+			if let descriptiveName = missingROM.descriptiveName {
+				requestLines.append("• " + descriptiveName)
+			} else {
+				requestLines.append("• " + missingROM.fileName)
+			}
+		}
+
+		// Suffix everything up to the penultimate line with a semicolon;
+		// the penultimate line with a semicolon and a conjunctive; the final
+		// line with a full stop.
+		for x in 0 ..< requestLines.count {
+			if x < requestLines.count - 2 {
+				requestLines[x].append(";")
+			} else if x < requestLines.count - 1 {
+				requestLines[x].append("; and")
+			} else {
+				requestLines[x].append(".")
+			}
+		}
+		romRequesterText!.stringValue = self.romRequestBaseText + requestLines.joined(separator: "\n")
+	}
+
+	func romReceiverView(_ view: CSROMReceiverView, didReceiveFileAt URL: URL) {
+		// Test whether the file identified matches any of the currently missing ROMs.
+		// If so then remove that ROM from the missing list and update the request screen.
+		// If no ROMs are still missing, start the machine.
+		do {
+			let fileData = try Data(contentsOf: URL)
+			var didInstallRom = false
+
+			// Try to match by size first, CRC second. Accept that some ROMs may have
+			// some additional appended data. Arbitrarily allow them to be up to 10kb
+			// too large.
+			var index = 0
+			for missingROM in self.missingROMs {
+				if fileData.count >= missingROM.size && fileData.count < missingROM.size + 10*1024 {
+					// Trim to size.
+					let trimmedData = fileData[0 ..< missingROM.size]
+
+					// Get CRC.
+					if missingROM.crc32s.contains( (trimmedData as NSData).crc32 ) {
+						// This ROM matches; copy it into the application library,
+						// strike it from the missing ROM list and decide how to
+						// proceed.
+						let fileManager = FileManager.default
+						let targetPath = fileManager.urls(for: .applicationSupportDirectory, in: .userDomainMask)[0]
+							.appendingPathComponent("ROMImages")
+							.appendingPathComponent(missingROM.machineName)
+						let targetFile = targetPath
+							.appendingPathComponent(missingROM.fileName)
+
+						do {
+							try fileManager.createDirectory(atPath: targetPath.path, withIntermediateDirectories: true, attributes: nil)
+							try trimmedData.write(to: targetFile)
+						} catch let error {
+							showRomReceiverError(error: "Couldn't write to application support directory: \(error)")
+						}
+
+						self.missingROMs.remove(at: index)
+						didInstallRom = true
+						break
+					}
+				}
+
+				index = index + 1
+			}
+
+			if didInstallRom {
+				if self.missingROMs.count == 0 {
+					self.windowControllers[0].window?.endSheet(self.romRequesterPanel!)
+					configureAs(self.selectedMachine!)
+				} else {
+					populateMissingRomList()
+				}
+			} else {
+				showRomReceiverError(error: "Didn't recognise contents of \(URL.lastPathComponent)")
+			}
+		} catch let error {
+			showRomReceiverError(error: "Couldn't read file at \(URL.absoluteString): \(error)")
+		}
+	}
+
+	// Yucky ugliness follows; my experience as an iOS developer intersects poorly with
+	// NSAnimationContext hence the various stateful diplications below. isShowingError
+	// should be essentially a duplicate of the current alphaValue, and animationCount
+	// is to resolve my inability to figure out how to cancel scheduled animations.
+	private var errorText = ""
+	private var isShowingError = false
+	private var animationCount = 0
+	private func showRomReceiverError(error: String) {
+		// Set or append the new error.
+		if self.errorText.count > 0 {
+			self.errorText = self.errorText + "\n" + error
+		} else {
+			self.errorText = error
+		}
+
+		// Apply the new complete text.
+		romReceiverErrorField!.stringValue = self.errorText
+
+		if !isShowingError {
+			// Schedule the box's appearance.
+			NSAnimationContext.beginGrouping()
+			NSAnimationContext.current.duration = 0.1
+			romReceiverErrorField?.animator().alphaValue = 1.0
+			NSAnimationContext.endGrouping()
+			isShowingError = true
+		}
+
+		// Schedule the box to disappear.
+		self.animationCount = self.animationCount + 1
+		let capturedAnimationCount = animationCount
+		DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + .seconds(2)) {
+			if self.animationCount == capturedAnimationCount {
+				NSAnimationContext.beginGrouping()
+				NSAnimationContext.current.duration = 1.0
+				self.romReceiverErrorField?.animator().alphaValue = 0.0
+				NSAnimationContext.endGrouping()
+				self.isShowingError = false
+				self.errorText = ""
+			}
+		}
+	}
+
 	// MARK: Joystick-via-the-keyboard selection
 	@IBAction func useKeyboardAsKeyboard(_ sender: NSMenuItem?) {
 		machine.inputMode = .keyboard
--- a/OSBindings/Mac/Clock
+++ b/OSBindings/Mac/Clock
@ -509,6 +509,10 @@
 			</array>
 			<key>CFBundleTypeIconFile</key>
 			<string>floppy35</string>
+			<key>CFBundleTypeMIMETypes</key>
+			<array>
+				<string>application/x-apple-diskimage</string>
+			</array>
 			<key>CFBundleTypeName</key>
 			<string>DiskCopy 4.2 Disk Image</string>
 			<key>CFBundleTypeOSTypes</key>
--- a/Signal/Machine/CSMachine.h
+++ b/Signal/Machine/CSMachine.h
@ -33,6 +33,14 @@ typedef NS_ENUM(NSInteger, CSMachineKeyboardInputMode) {
 	CSMachineKeyboardInputModeJoystick
 };

+@interface CSMissingROM: NSObject
+@property (nonatomic, readonly, nonnull) NSString *machineName;
+@property (nonatomic, readonly, nonnull) NSString *fileName;
+@property (nonatomic, readonly, nullable) NSString *descriptiveName;
+@property (nonatomic, readonly) NSUInteger size;
+@property (nonatomic, readonly, nonnull) NSArray<NSNumber *> *crc32s;
+@end
+
 // Deliberately low; to ensure CSMachine has been declared as an @class already.
 #import "CSAtari2600.h"
 #import "CSZX8081.h"
@ -45,8 +53,10 @@ typedef NS_ENUM(NSInteger, CSMachineKeyboardInputMode) {
 	Initialises an instance of CSMachine.

 	@param result The CSStaticAnalyser result that describes the machine needed.
+	@param missingROMs An array that is filled with a list of ROMs that the machine requested but which
+		were not found; populated only if this `init` has failed.
 */
- (nullable instancetype)initWithAnalyser:(nonnull CSStaticAnalyser *)result NS_DESIGNATED_INITIALIZER;
+- (nullable instancetype)initWithAnalyser:(nonnull CSStaticAnalyser *)result missingROMs:(nullable inout NSMutableArray<CSMissingROM *> *)missingROMs NS_DESIGNATED_INITIALIZER;

 - (void)runForInterval:(NSTimeInterval)interval;

--- a/Signal/Machine/CSMachine.mm
+++ b/Signal/Machine/CSMachine.mm
@ -74,6 +74,68 @@ struct ActivityObserver: public Activity::Observer {
 	__unsafe_unretained CSMachine *machine;
 };

+@interface CSMissingROM (Mutability)
+@property (nonatomic, nonnull, copy) NSString *machineName;
+@property (nonatomic, nonnull, copy) NSString *fileName;
+@property (nonatomic, nullable, copy) NSString *descriptiveName;
+@property (nonatomic, readwrite) NSUInteger size;
+@property (nonatomic, copy) NSArray<NSNumber *> *crc32s;
+@end
+
+@implementation CSMissingROM {
+	NSString *_machineName;
+	NSString *_fileName;
+	NSString *_descriptiveName;
+	NSUInteger _size;
+	NSArray<NSNumber *> *_crc32s;
+}
+
+- (NSString *)machineName {
+	return _machineName;
+}
+
+- (void)setMachineName:(NSString *)machineName {
+	_machineName = [machineName copy];
+}
+
+- (NSString *)fileName {
+	return _fileName;
+}
+
+- (void)setFileName:(NSString *)fileName {
+	_fileName = [fileName copy];
+}
+
+- (NSString *)descriptiveName {
+	return _descriptiveName;
+}
+
+- (void)setDescriptiveName:(NSString *)descriptiveName {
+	_descriptiveName = [descriptiveName copy];
+}
+
+- (NSUInteger)size {
+	return _size;
+}
+
+- (void)setSize:(NSUInteger)size {
+	_size = size;
+}
+
+- (NSArray<NSNumber *> *)crc32s {
+	return _crc32s;
+}
+
+- (void)setCrc32s:(NSArray<NSNumber *> *)crc32s {
+	_crc32s = [crc32s copy];
+}
+
+- (NSString *)description {
+	return [NSString stringWithFormat:@"%@/%@, %@ bytes, CRCs: %@", _fileName, _descriptiveName, @(_size), _crc32s];
+}
+
+@end
+
@implementation CSMachine {
 	SpeakerDelegate _speakerDelegate;
 	ActivityObserver _activityObserver;
@ -90,14 +152,37 @@ struct ActivityObserver: public Activity::Observer {
 	std::unique_ptr<Outputs::Display::OpenGL::ScanTarget> _scanTarget;
 }

- (instancetype)initWithAnalyser:(CSStaticAnalyser *)result {
+- (instancetype)initWithAnalyser:(CSStaticAnalyser *)result missingROMs:(inout NSMutableArray<CSMissingROM *> *)missingROMs {
 	self = [super init];
 	if(self) {
 		_analyser = result;

 		Machine::Error error;
-		_machine.reset(Machine::MachineForTargets(_analyser.targets, CSROMFetcher(), error));
-		if(!_machine) return nil;
+		std::vector<ROMMachine::ROM> missing_roms;
+		_machine.reset(Machine::MachineForTargets(_analyser.targets, CSROMFetcher(&missing_roms), error));
+		if(!_machine) {
+			for(const auto &missing_rom : missing_roms) {
+				CSMissingROM *rom = [[CSMissingROM alloc] init];
+
+				// Copy/convert the primitive fields.
+				rom.machineName = [NSString stringWithUTF8String:missing_rom.machine_name.c_str()];
+				rom.fileName = [NSString stringWithUTF8String:missing_rom.file_name.c_str()];
+				rom.descriptiveName = missing_rom.descriptive_name.empty() ? nil : [NSString stringWithUTF8String:missing_rom.descriptive_name.c_str()];
+				rom.size = missing_rom.size;
+
+				// Convert the CRC list.
+				NSMutableArray<NSNumber *> *crc32s = [[NSMutableArray alloc] init];
+				for(const auto &crc : missing_rom.crc32s) {
+					[crc32s addObject:@(crc)];
+				}
+				rom.crc32s = [crc32s copy];
+
+				// Add to the missing list.
+				[missingROMs addObject:rom];
+			}
+
+			return nil;
+		}

 		_inputMode =
 			(_machine->keyboard_machine() && _machine->keyboard_machine()->get_keyboard().is_exclusive())
--- a/Signal/Machine/CSROMFetcher.hpp
+++ b/Signal/Machine/CSROMFetcher.hpp
@ -8,4 +8,4 @@

 #include "ROMMachine.hpp"

-ROMMachine::ROMFetcher CSROMFetcher();
+ROMMachine::ROMFetcher CSROMFetcher(std::vector<ROMMachine::ROM> *missing_roms = nullptr);
--- a/Signal/Machine/CSROMFetcher.mm
+++ b/Signal/Machine/CSROMFetcher.mm
@ -14,15 +14,39 @@

 #include <string>

-ROMMachine::ROMFetcher CSROMFetcher() {
-	return [] (const std::string &machine, const std::vector<std::string> &names) -> std::vector<std::unique_ptr<std::vector<std::uint8_t>>> {
-		NSString *subDirectory = [@"ROMImages/" stringByAppendingString:[NSString stringWithUTF8String:machine.c_str()]];
-		std::vector<std::unique_ptr<std::vector<std::uint8_t>>> results;
-		for(const auto &name: names) {
-			NSData *fileData = [[NSBundle mainBundle] dataForResource:[NSString stringWithUTF8String:name.c_str()] withExtension:nil subdirectory:subDirectory];
+ROMMachine::ROMFetcher CSROMFetcher(std::vector<ROMMachine::ROM> *missing_roms) {
+	return [missing_roms] (const std::vector<ROMMachine::ROM> &roms) -> std::vector<std::unique_ptr<std::vector<std::uint8_t>>> {
+		NSArray<NSURL *> *const supportURLs = [[NSFileManager defaultManager] URLsForDirectory:NSApplicationSupportDirectory inDomains:NSUserDomainMask];

-			if(!fileData)
+		std::vector<std::unique_ptr<std::vector<std::uint8_t>>> results;
+		for(const auto &rom: roms) {
+			NSData *fileData;
+			NSString *const subdirectory = [@"ROMImages/" stringByAppendingString:[NSString stringWithUTF8String:rom.machine_name.c_str()]];
+
+			// Check for this file first within the application support directories.
+			for(NSURL *supportURL in supportURLs) {
+				NSURL *const fullURL = [[supportURL URLByAppendingPathComponent:subdirectory]
+							URLByAppendingPathComponent:[NSString stringWithUTF8String:rom.file_name.c_str()]];
+				fileData = [NSData dataWithContentsOfURL:fullURL];
+				if(fileData) break;
+			}
+
+			// Failing that, check inside the application bundle.
+			if(!fileData) {
+				fileData = [[NSBundle mainBundle]
+					dataForResource:[NSString stringWithUTF8String:rom.file_name.c_str()]
+					withExtension:nil
+					subdirectory:subdirectory];
+			}
+
+			// Store an appropriate result, accumulating a list of the missing if requested.
+			if(!fileData) {
 				results.emplace_back(nullptr);
+
+				if(missing_roms) {
+					missing_roms->push_back(rom);
+				}
+			}
 			else {
 				std::unique_ptr<std::vector<std::uint8_t>> data(new std::vector<std::uint8_t>);
 				*data = fileData.stdVector8;
--- a/Signal/Machine/NSData+CRC32.h
+++ b/Signal/Machine/NSData+CRC32.h
@ -0,0 +1,17 @@
+//
+//  NSData+CRC32.m
+//  Clock Signal
+//
+//  Created by Thomas Harte on 22/07/2019.
+//  Copyright 2019 Thomas Harte. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+#include <stdint.h>
+
+@interface NSData (CRC32)
+
+@property(nonnull, nonatomic, readonly) NSNumber *crc32;
+
+@end
--- a/Signal/Machine/NSData+CRC32.m
+++ b/Signal/Machine/NSData+CRC32.m
@ -0,0 +1,19 @@
+//
+//  NSData+CRC32.m
+//  Clock Signal
+//
+//  Created by Thomas Harte on 22/07/2019.
+//  Copyright 2019 Thomas Harte. All rights reserved.
+//
+
+#import "NSData+CRC32.h"
+
+#include <zlib.h>
+
+@implementation NSData (StdVector)
+
+- (NSNumber *)crc32 {
+    return @(crc32(crc32(0, Z_NULL, 0), self.bytes, (uInt)self.length));
+}
+
+@end
--- a/Signal/MachinePicker/Base.lproj/MachinePicker.xib
+++ b/Signal/MachinePicker/Base.lproj/MachinePicker.xib
@ -64,7 +64,7 @@ Gw
                        <tabViewItems>
                            <tabViewItem label="Apple II" identifier="appleii" id="P59-QG-LOa">
                                <view key="view" id="dHz-Yv-GNq">
-                                    <rect key="frame" x="10" y="33" width="554" height="94"/>
+                                    <rect key="frame" x="10" y="33" width="604" height="94"/>
                                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                                    <subviews>
                                        <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="V5Z-dX-Ns4">
@ -168,7 +168,7 @@ Gw
                            </tabViewItem>
                            <tabViewItem label="Electron" identifier="electron" id="muc-z9-Vqc">
                                <view key="view" id="SRc-2D-95G">
-                                    <rect key="frame" x="10" y="33" width="654" height="94"/>
+                                    <rect key="frame" x="10" y="33" width="604" height="94"/>
                                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                                    <subviews>
                                        <button verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="JqM-IK-FMP">
@ -199,13 +199,29 @@ Gw
                            </tabViewItem>
                            <tabViewItem label="Macintosh" identifier="mac" id="lmR-z3-xSm">
                                <view key="view" id="7Yf-vi-Q0W">
-                                    <rect key="frame" x="10" y="33" width="654" height="94"/>
+                                    <rect key="frame" x="10" y="33" width="604" height="94"/>
                                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                    <subviews>
+                                        <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="F6e-UC-25u">
+                                            <rect key="frame" x="15" y="74" width="574" height="17"/>
+                                            <textFieldCell key="cell" lineBreakMode="clipping" title="At present Clock Signal emulates only the Macintosh 512ke." id="IGV-Yp-6Af">
+                                                <font key="font" usesAppearanceFont="YES"/>
+                                                <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                        </textField>
+                                    </subviews>
+                                    <constraints>
+                                        <constraint firstAttribute="trailing" secondItem="F6e-UC-25u" secondAttribute="trailing" constant="17" id="42z-hS-aPq"/>
+                                        <constraint firstItem="F6e-UC-25u" firstAttribute="leading" secondItem="7Yf-vi-Q0W" secondAttribute="leading" constant="17" id="bIg-C3-xdz"/>
+                                        <constraint firstItem="F6e-UC-25u" firstAttribute="top" secondItem="7Yf-vi-Q0W" secondAttribute="top" constant="3" id="cxs-OP-oH5"/>
+                                        <constraint firstAttribute="bottom" relation="greaterThanOrEqual" secondItem="F6e-UC-25u" secondAttribute="bottom" constant="17" id="vpF-ER-pmD"/>
+                                    </constraints>
                                </view>
                            </tabViewItem>
                            <tabViewItem label="MSX" identifier="msx" id="6SR-DY-zdI">
                                <view key="view" id="mWD-An-tR7">
-                                    <rect key="frame" x="10" y="33" width="654" height="94"/>
+                                    <rect key="frame" x="10" y="33" width="604" height="94"/>
                                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                                    <subviews>
                                        <button verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="8xT-Pr-8SE">
@ -253,7 +269,7 @@ Gw
                            </tabViewItem>
                            <tabViewItem label="Oric" identifier="oric" id="NSx-DC-p4M">
                                <view key="view" id="sOR-e0-8iZ">
-                                    <rect key="frame" x="10" y="33" width="654" height="94"/>
+                                    <rect key="frame" x="10" y="33" width="604" height="94"/>
                                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                                    <subviews>
                                        <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="0ct-tf-uRH">
@ -318,7 +334,7 @@ Gw
                            </tabViewItem>
                            <tabViewItem label="Vic-20" identifier="vic20" id="cyO-PU-hSU">
                                <view key="view" id="fLI-XB-QCr">
-                                    <rect key="frame" x="10" y="33" width="554" height="94"/>
+                                    <rect key="frame" x="10" y="33" width="604" height="94"/>
                                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                                    <subviews>
                                        <popUpButton verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="ueK-gq-gaF">
@ -497,7 +513,7 @@ Gw
                    <constraint firstItem="VUb-QG-x7c" firstAttribute="top" secondItem="EiT-Mj-1SZ" secondAttribute="top" constant="20" id="zT3-Ea-QQJ"/>
                </constraints>
            </view>
-            <point key="canvasLocation" x="34" y="89"/>
+            <point key="canvasLocation" x="34" y="88.5"/>
        </window>
        <customObject id="192-Eb-Rpg" customClass="MachinePicker" customModule="Clock_Signal" customModuleProvider="target">
            <connections>
--- a/Signal/ROMRequester/CSROMReceiverView.h
+++ b/Signal/ROMRequester/CSROMReceiverView.h
@ -0,0 +1,27 @@
+//
+//  CSROMReceiverView.h
+//  Clock Signal
+//
+//  Created by Thomas Harte on 22/07/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#import <Cocoa/Cocoa.h>
+
+@class CSROMReceiverView;
+
+@protocol CSROMReciverViewDelegate
+/*!
+	Announces receipt of a file by drag and drop to the delegate.
+	@param view The view making the request.
+	@param URL The file URL of the received file.
+*/
+- (void)romReceiverView:(nonnull CSROMReceiverView *)view didReceiveFileAtURL:(nonnull NSURL *)URL;
+
+@end
+
+@interface CSROMReceiverView : NSView
+
+@property(nonatomic, weak, nullable) id <CSROMReciverViewDelegate> delegate;
+
+@end
--- a/Signal/ROMRequester/CSROMReceiverView.m
+++ b/Signal/ROMRequester/CSROMReceiverView.m
@ -0,0 +1,40 @@
+//
+//  CSROMReceiverView.m
+//  Clock Signal
+//
+//  Created by Thomas Harte on 22/07/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#import "CSROMReceiverView.h"
+
+@interface CSROMReceiverView () <NSDraggingDestination>
+@end
+
+
+@implementation CSROMReceiverView
+
+- (void)awakeFromNib {
+	[super awakeFromNib];
+
+	// Accept file URLs by drag and drop.
+	[self registerForDraggedTypes:@[(__bridge NSString *)kUTTypeFileURL]];
+}
+
+#pragma mark - NSDraggingDestination
+
+- (BOOL)performDragOperation:(id <NSDraggingInfo>)sender {
+	// Just forward the URLs.
+	for(NSPasteboardItem *item in [[sender draggingPasteboard] pasteboardItems]) {
+		NSURL *URL = [NSURL URLWithString:[item stringForType:(__bridge NSString *)kUTTypeFileURL]];
+		[self.delegate romReceiverView:self didReceiveFileAtURL:URL];
+	}
+	return YES;
+}
+
+- (NSDragOperation)draggingEntered:(id < NSDraggingInfo >)sender {
+	// The emulator will take a copy of any deposited ROM files.
+	return NSDragOperationCopy;
+}
+
+@end
--- a/Signal/ROMRequester/ROMRequester.xib
+++ b/Signal/ROMRequester/ROMRequester.xib
@ -0,0 +1,75 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="14490.70" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
+    <dependencies>
+        <deployment identifier="macosx"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="14490.70"/>
+        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
+    </dependencies>
+    <objects>
+        <customObject id="-2" userLabel="File's Owner" customClass="MachineDocument" customModule="Clock_Signal" customModuleProvider="target">
+            <connections>
+                <outlet property="romReceiverErrorField" destination="Bia-0m-GxK" id="wnH-Kz-uXD"/>
+                <outlet property="romReceiverView" destination="EiT-Mj-1SZ" id="Y2M-Qd-i7y"/>
+                <outlet property="romRequesterPanel" destination="QvC-M9-y7g" id="saI-YH-9NP"/>
+                <outlet property="romRequesterText" destination="5qG-I3-Qav" id="J9M-T8-Xyy"/>
+            </connections>
+        </customObject>
+        <customObject id="-1" userLabel="First Responder" customClass="FirstResponder"/>
+        <customObject id="-3" userLabel="Application" customClass="NSObject"/>
+        <window title="Window" allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" releasedWhenClosed="NO" visibleAtLaunch="NO" animationBehavior="default" titleVisibility="hidden" id="QvC-M9-y7g">
+            <windowStyleMask key="styleMask" titled="YES"/>
+            <windowPositionMask key="initialPositionMask" leftStrut="YES" rightStrut="YES" topStrut="YES" bottomStrut="YES"/>
+            <rect key="contentRect" x="196" y="240" width="480" height="270"/>
+            <rect key="screenRect" x="0.0" y="0.0" width="1440" height="900"/>
+            <view key="contentView" wantsLayer="YES" id="EiT-Mj-1SZ" customClass="CSROMReceiverView">
+                <rect key="frame" x="0.0" y="0.0" width="480" height="270"/>
+                <autoresizingMask key="autoresizingMask"/>
+                <subviews>
+                    <textField verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" textCompletion="NO" translatesAutoresizingMaskIntoConstraints="NO" id="5qG-I3-Qav">
+                        <rect key="frame" x="18" y="148" width="444" height="102"/>
+                        <textFieldCell key="cell" enabled="NO" allowsUndo="NO" id="itJ-2T-0ia">
+                            <font key="font" usesAppearanceFont="YES"/>
+                            <string key="title">Clock Signal requires you to provide images of the system ROMs for this machine. They will be stored permanently; you need do this only once.  Please drag and drop the following over this view:
+
+</string>
+                            <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                            <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                        </textFieldCell>
+                    </textField>
+                    <button verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="nvl-dm-8bK">
+                        <rect key="frame" x="384" y="13" width="82" height="32"/>
+                        <buttonCell key="cell" type="push" title="Cancel" bezelStyle="rounded" alignment="center" borderStyle="border" imageScaling="proportionallyDown" inset="2" id="oS1-Pk-LsO">
+                            <behavior key="behavior" pushIn="YES" lightByBackground="YES" lightByGray="YES"/>
+                            <font key="font" metaFont="system"/>
+                            <string key="keyEquivalent" base64-UTF8="YES">
+DQ
+</string>
+                        </buttonCell>
+                        <connections>
+                            <action selector="cancelRequestROMs:" target="-2" id="58q-yi-dlv"/>
+                        </connections>
+                    </button>
+                    <textField verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" textCompletion="NO" translatesAutoresizingMaskIntoConstraints="NO" id="Bia-0m-GxK">
+                        <rect key="frame" x="20" y="61" width="442" height="17"/>
+                        <textFieldCell key="cell" allowsUndo="NO" alignment="center" title="Multiline Label" drawsBackground="YES" id="8jl-xs-LjP">
+                            <font key="font" metaFont="message"/>
+                            <color key="textColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                            <color key="backgroundColor" name="tertiaryLabelColor" catalog="System" colorSpace="catalog"/>
+                        </textFieldCell>
+                    </textField>
+                </subviews>
+                <constraints>
+                    <constraint firstItem="Bia-0m-GxK" firstAttribute="leading" secondItem="EiT-Mj-1SZ" secondAttribute="leading" constant="20" id="9Lj-3p-7Vr"/>
+                    <constraint firstAttribute="trailing" secondItem="5qG-I3-Qav" secondAttribute="trailing" constant="20" id="AwT-WO-Nyf"/>
+                    <constraint firstAttribute="bottom" secondItem="nvl-dm-8bK" secondAttribute="bottom" constant="20" id="BU0-5T-YRH"/>
+                    <constraint firstAttribute="bottom" secondItem="Bia-0m-GxK" secondAttribute="bottom" constant="61" id="ENn-7a-NGa"/>
+                    <constraint firstAttribute="trailing" secondItem="Bia-0m-GxK" secondAttribute="trailing" constant="18" id="UUy-bf-87w"/>
+                    <constraint firstItem="5qG-I3-Qav" firstAttribute="leading" secondItem="EiT-Mj-1SZ" secondAttribute="leading" constant="20" id="bRM-z1-cRf"/>
+                    <constraint firstAttribute="trailing" secondItem="nvl-dm-8bK" secondAttribute="trailing" constant="20" id="eQI-Nj-ane"/>
+                    <constraint firstItem="nvl-dm-8bK" firstAttribute="top" relation="greaterThanOrEqual" secondItem="5qG-I3-Qav" secondAttribute="bottom" constant="17" id="plB-x4-He5"/>
+                    <constraint firstItem="5qG-I3-Qav" firstAttribute="top" secondItem="EiT-Mj-1SZ" secondAttribute="top" constant="20" id="qeC-Rh-hmr"/>
+                </constraints>
+            </view>
+        </window>
+    </objects>
+</document>
--- a/OSBindings/SDL/main.cpp
+++ b/OSBindings/SDL/main.cpp
@ -9,6 +9,7 @@
 #include <algorithm>
 #include <array>
 #include <cstdio>
+#include <cstdlib>
 #include <cstring>
 #include <iostream>
 #include <memory>
@ -339,21 +340,21 @@ int main(int argc, char *argv[]) {
 			}
 			std::cout << std::endl;
 		}
-		return 0;
+		return EXIT_SUCCESS;
 	}

 	// Perform a sanity check on arguments.
 	if(arguments.file_name.empty()) {
 		std::cerr << "Usage: " << final_path_component(argv[0]) << usage_suffix << std::endl;
 		std::cerr << "Use --help to learn more about available options." << std::endl;
-		return -1;
+		return EXIT_FAILURE;
 	}

 	// Determine the machine for the supplied file.
 	Analyser::Static::TargetList targets = Analyser::Static::GetTargets(arguments.file_name);
 	if(targets.empty()) {
 		std::cerr << "Cannot open " << arguments.file_name << "; no target machine found" << std::endl;
-		return -1;
+		return EXIT_FAILURE;
 	}

 	Concurrency::BestEffortUpdater updater;
@ -365,12 +366,10 @@ int main(int argc, char *argv[]) {
 	//	/usr/local/share/CLK/[system];
 	//	/usr/share/CLK/[system]; or
 	//	[user-supplied path]/[system]
-	std::vector<std::string> rom_names;
-	std::string machine_name;
-	ROMMachine::ROMFetcher rom_fetcher = [&rom_names, &machine_name, &arguments]
-		(const std::string &machine, const std::vector<std::string> &names) -> std::vector<std::unique_ptr<std::vector<uint8_t>>> {
-			rom_names.insert(rom_names.end(), names.begin(), names.end());
-			machine_name = machine;
+	std::vector<ROMMachine::ROM> requested_roms;
+	ROMMachine::ROMFetcher rom_fetcher = [&requested_roms, &arguments]
+		(const std::vector<ROMMachine::ROM> &roms) -> std::vector<std::unique_ptr<std::vector<uint8_t>>> {
+			requested_roms.insert(requested_roms.end(), roms.begin(), roms.end());

 			std::vector<std::string> paths = {
 				"/usr/local/share/CLK/",
@ -386,10 +385,10 @@ int main(int argc, char *argv[]) {
 			}

 			std::vector<std::unique_ptr<std::vector<uint8_t>>> results;
-			for(const auto &name: names) {
+			for(const auto &rom: roms) {
 				FILE *file = nullptr;
 				for(const auto &path: paths) {
-					std::string local_path = path + machine + "/" + name;
+					std::string local_path = path + rom.machine_name + "/" + rom.file_name;
 					file = std::fopen(local_path.c_str(), "rb");
 					if(file) break;
 				}
@ -425,13 +424,17 @@ int main(int argc, char *argv[]) {
 			case ::Machine::Error::MissingROM:
 				std::cerr << "Could not find system ROMs; please install to /usr/local/share/CLK/ or /usr/share/CLK/, or provide a --rompath." << std::endl;
 				std::cerr << "One or more of the following was needed but not found:" << std::endl;
-				for(const auto &name: rom_names) {
-					std::cerr << machine_name << '/' << name << std::endl;
+				for(const auto &rom: requested_roms) {
+					std::cerr << rom.machine_name << '/' << rom.file_name;
+					if(!rom.descriptive_name.empty()) {
+						std::cerr << " (" << rom.descriptive_name << ")";
+					}
+					std::cerr << std::endl;
 				}
 			break;
 		}

-		return -1;
+		return EXIT_FAILURE;
 	}

 	best_effort_updater_delegate.machine = machine.get();
@ -441,7 +444,7 @@ int main(int argc, char *argv[]) {
 	// Attempt to set up video and audio.
 	if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO) < 0) {
 		std::cerr << "SDL could not initialize! SDL_Error: " << SDL_GetError() << std::endl;
-		return -1;
+		return EXIT_FAILURE;
 	}

 	// Ask for no depth buffer, a core profile and vsync-aligned rendering.
@ -463,7 +466,7 @@ int main(int argc, char *argv[]) {
 	if(!window || !gl_context) {
 		std::cerr << "Could not create " << (window ? "OpenGL context" : "window");
 		std::cerr << "; reported error: \"" << SDL_GetError() << "\"" << std::endl;
-		return -1;
+		return EXIT_FAILURE;
 	}

 	SDL_GL_MakeCurrent(window, gl_context);
@ -816,5 +819,5 @@ int main(int argc, char *argv[]) {
 	SDL_DestroyWindow( window );
 	SDL_Quit();

-	return 0;
+	return EXIT_SUCCESS;
 }