Made an attempt at correct timing, adding support for additional paged ROMs, added file association for .rom.

Machines/Electron/Electron.cpp

@@ -27,6 +27,8 @@ Machine::Machine() :
 	memset(_palette, 0xf, sizeof(_palette));
 	_crt = new Outputs::CRT(crt_cycles_per_line, 312, 1, 1);
 	_interruptStatus = 0x02;
+	for(int c = 0; c < 16; c++)
+		memset(_roms[c], 0xff, 16384);
 	setup6502();
 }
 
@@ -55,6 +57,13 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 
 		// TODO: RAM timing for Modes 0–3
 		cycles += (_frameCycles&1)^1;
+		if(_screenMode < 4)
+		{
+			const int current_line = _frameCycles >> 7;
+			const int line_position = _frameCycles & 127;
+			if(current_line >= 28 && current_line < 28+256 && line_position >= 24 && line_position < 104)
+				cycles = (unsigned int)(104 - line_position);
+		}
 	}
 	else
 	{
@@ -191,10 +200,6 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 			{
 				switch(_activeRom)
 				{
-					case ROMSlotBASIC:
-					case ROMSlotBASIC+1:
-						*value = _basic[address & 16383];
-					break;
 					case ROMSlotKeyboard:
 					case ROMSlotKeyboard+1:
 						*value = 0xf0;
@@ -204,7 +209,7 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 						}
 					break;
 					default:
-						*value = 0xff;
+						*value = _roms[_activeRom][address & 16383];
 					break;
 				}
 			}
@@ -235,9 +240,8 @@ void Machine::set_rom(ROMSlot slot, size_t length, const uint8_t *data)
 	uint8_t *target = nullptr;
 	switch(slot)
 	{
-		case ROMSlotBASIC:	target = _basic;	break;
 		case ROMSlotOS:		target = _os;			break;
-		default: return;
+		default:			target = _roms[slot];	break;
 	}
 
 	memcpy(target, data, std::min((size_t)16384, length));

Machines/Electron/Electron.hpp

@@ -73,7 +73,8 @@ class Machine: public CPU6502::Processor<Machine> {
 		const char *get_signal_decoder();
 
 	private:
-		uint8_t _os[16384], _basic[16384], _ram[32768];
+		uint8_t _roms[16][16384];
+		uint8_t _os[16384], _ram[32768];
 		uint8_t _interruptStatus, _interruptControl;
 		uint8_t _palette[16];
 		uint8_t _keyStates[14];

OSBindings/Mac/Clock Signal/Documents/ElectronDocument.swift

@@ -34,6 +34,7 @@ class ElectronDocument: MachineDocument {
 	}
 
 	override func readFromData(data: NSData, ofType typeName: String) throws {
+		electron.setROM(data, slot: 15)
 	}
 
 	// MARK: CSOpenGLViewDelegate

OSBindings/Mac/Clock Signal/Info.plist

@@ -41,6 +41,20 @@
 			<key>NSDocumentClass</key>
 			<string>$(PRODUCT_MODULE_NAME).ElectronDocument</string>
 		</dict>
+		<dict>
+			<key>CFBundleTypeExtensions</key>
+			<array>
+				<string>rom</string>
+			</array>
+			<key>CFBundleTypeName</key>
+			<string>Electron/BBC ROM Image</string>
+			<key>CFBundleTypeRole</key>
+			<string>Viewer</string>
+			<key>LSTypeIsPackage</key>
+			<integer>0</integer>
+			<key>NSDocumentClass</key>
+			<string>$(PRODUCT_MODULE_NAME).ElectronDocument</string>
+		</dict>
 	</array>
 	<key>CFBundleExecutable</key>
 	<string>$(EXECUTABLE_NAME)</string>

OSBindings/Mac/Clock Signal/Wrappers/CSElectron.h

@@ -13,6 +13,7 @@
 
 - (void)setOSROM:(nonnull NSData *)rom;
 - (void)setBASICROM:(nonnull NSData *)rom;
+- (void)setROM:(nonnull NSData *)rom slot:(int)slot;
 
 - (void)setKey:(uint16_t)key isPressed:(BOOL)isPressed;
 

OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm

@@ -27,7 +27,11 @@
 	_electron.set_rom(Electron::ROMSlotBASIC, rom.length, (const uint8_t *)rom.bytes);
 }
 
-- (void)setCRTDelegate:(Outputs::CRT::Delegate *)delegate{
+- (void)setROM:(nonnull NSData *)rom slot:(int)slot {
+	_electron.set_rom((Electron::ROMSlot)slot, rom.length, (const uint8_t *)rom.bytes);
+}
+
+- (void)setCRTDelegate:(Outputs::CRT::Delegate *)delegate {
 	_electron.get_crt()->set_delegate(delegate);
 }