diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 3728929e5..6628b060a 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -357,6 +357,7 @@
 		4BF1354C1D6D2C300054B2EA /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BF1354A1D6D2C300054B2EA /* StaticAnalyser.cpp */; };
 		4BF8295D1D8F048B001BAE39 /* MFM.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BF8295B1D8F048B001BAE39 /* MFM.cpp */; };
 		4BF829601D8F3C87001BAE39 /* CRC.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BF8295E1D8F3C87001BAE39 /* CRC.cpp */; };
+		4BF829631D8F536B001BAE39 /* SSD.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BF829611D8F536B001BAE39 /* SSD.cpp */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -811,6 +812,8 @@
 		4BF8295C1D8F048B001BAE39 /* MFM.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = MFM.hpp; path = Encodings/MFM.hpp; sourceTree = "<group>"; };
 		4BF8295E1D8F3C87001BAE39 /* CRC.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = CRC.cpp; path = ../../NumberTheory/CRC.cpp; sourceTree = "<group>"; };
 		4BF8295F1D8F3C87001BAE39 /* CRC.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = CRC.hpp; path = ../../NumberTheory/CRC.hpp; sourceTree = "<group>"; };
+		4BF829611D8F536B001BAE39 /* SSD.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = SSD.cpp; sourceTree = "<group>"; };
+		4BF829621D8F536B001BAE39 /* SSD.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = SSD.hpp; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -1117,6 +1120,8 @@
 				4BAB62B41D327F7E00DF5BA0 /* G64.hpp */,
 				4B4C836E1D4F623200CD541F /* D64.cpp */,
 				4B4C836F1D4F623200CD541F /* D64.hpp */,
+				4BF829611D8F536B001BAE39 /* SSD.cpp */,
+				4BF829621D8F536B001BAE39 /* SSD.hpp */,
 			);
 			path = Formats;
 			sourceTree = "<group>";
@@ -2112,6 +2117,7 @@
 				4B643F3A1D77AD1900D431D6 /* CSStaticAnalyser.mm in Sources */,
 				4B4DC8281D2C2470003C5BF8 /* C1540.cpp in Sources */,
 				4B1E85751D170228001EF87D /* Typer.cpp in Sources */,
+				4BF829631D8F536B001BAE39 /* SSD.cpp in Sources */,
 				4B2E2D9D1C3A070400138695 /* Electron.cpp in Sources */,
 				4BAB62B81D3302CA00DF5BA0 /* PCMTrack.cpp in Sources */,
 				4B69FB3D1C4D908A00B5F0AA /* Tape.cpp in Sources */,
diff --git a/StaticAnalyser/StaticAnalyser.cpp b/StaticAnalyser/StaticAnalyser.cpp
index 2f57788f2..98d799b05 100644
--- a/StaticAnalyser/StaticAnalyser.cpp
+++ b/StaticAnalyser/StaticAnalyser.cpp
@@ -22,6 +22,7 @@
 // Disks
 #include "../Storage/Disk/Formats/D64.hpp"
 #include "../Storage/Disk/Formats/G64.hpp"
+#include "../Storage/Disk/Formats/SSD.hpp"
 
 // Tapes
 #include "../Storage/Tape/Formats/CommodoreTAP.hpp"
@@ -81,6 +82,7 @@ std::list<Target> StaticAnalyser::GetTargets(const char *file_name)
 	Format("a26", cartridges, Cartridge::BinaryDump, TargetPlatform::Atari2600)		// A26
 	Format("bin", cartridges, Cartridge::BinaryDump, TargetPlatform::Atari2600)		// BIN
 	Format("d64", disks, Disk::D64, TargetPlatform::Commodore)						// D64
+	Format("dsd", disks, Disk::SSD, TargetPlatform::Acorn)							// DSD
 	Format("g64", disks, Disk::G64, TargetPlatform::Commodore)						// G64
 
 	// PRG
@@ -98,8 +100,8 @@ std::list<Target> StaticAnalyser::GetTargets(const char *file_name)
 		}
 	}
 
-	// ROM
 	Format("rom", cartridges, Cartridge::BinaryDump, TargetPlatform::Acorn)		// ROM
+	Format("ssd", disks, Disk::SSD, TargetPlatform::Acorn)						// SSD
 	Format("tap", tapes, Tape::CommodoreTAP, TargetPlatform::Commodore)			// TAP
 	Format("uef", tapes, Tape::UEF, TargetPlatform::Acorn)						// UEF (tape)
 
diff --git a/Storage/Disk/Disk.hpp b/Storage/Disk/Disk.hpp
index c17712b85..50466161e 100644
--- a/Storage/Disk/Disk.hpp
+++ b/Storage/Disk/Disk.hpp
@@ -73,10 +73,15 @@ class Disk {
 		*/
 		virtual unsigned int get_head_position_count() = 0;
 
+		/*!
+			Returns the number of heads (and, therefore, impliedly surfaces) available on this disk.
+		*/
+		virtual unsigned int get_head_count() { return 1; }
+
 		/*!
 			Returns the @c Track at @c position if there are any detectable events there; returns @c nullptr otherwise.
 		*/
-		virtual std::shared_ptr<Track> get_track_at_position(unsigned int position) = 0;
+		virtual std::shared_ptr<Track> get_track_at_position(unsigned int head, unsigned int position) = 0;
 };
 
 }
diff --git a/Storage/Disk/DiskDrive.cpp b/Storage/Disk/DiskDrive.cpp
index 681a9e94d..f69788950 100644
--- a/Storage/Disk/DiskDrive.cpp
+++ b/Storage/Disk/DiskDrive.cpp
@@ -60,7 +60,7 @@ void Drive::step(int direction)
 
 void Drive::set_track(Time initial_offset)
 {
-	_track = _disk->get_track_at_position((unsigned int)_head_position);
+	_track = _disk->get_track_at_position(0, (unsigned int)_head_position);
 	// TODO: probably a better implementation of the empty track?
 	Time offset;
 	if(_track && _time_into_track.length > 0)
diff --git a/Storage/Disk/Encodings/MFM.cpp b/Storage/Disk/Encodings/MFM.cpp
index b8704946a..6b7bd7102 100644
--- a/Storage/Disk/Encodings/MFM.cpp
+++ b/Storage/Disk/Encodings/MFM.cpp
@@ -191,7 +191,7 @@ template<class T> std::shared_ptr<Storage::Disk::Track>
 
 	while(shifter.segment.data.size() < expected_track_bytes) shifter.add_byte(0x00);
 
-	shifter.segment.number_of_bits = shifter.segment.data.size() * 8;
+	shifter.segment.number_of_bits = (unsigned int)(shifter.segment.data.size() * 8);
 	return std::shared_ptr<Storage::Disk::Track>(new Storage::Disk::PCMTrack(std::move(shifter.segment)));
 }
 
diff --git a/Storage/Disk/Formats/D64.cpp b/Storage/Disk/Formats/D64.cpp
index af406c253..f0397b10b 100644
--- a/Storage/Disk/Formats/D64.cpp
+++ b/Storage/Disk/Formats/D64.cpp
@@ -53,10 +53,10 @@ unsigned int D64::get_head_position_count()
 	return _number_of_tracks*2;
 }
 
-std::shared_ptr<Track> D64::get_track_at_position(unsigned int position)
+std::shared_ptr<Track> D64::get_track_at_position(unsigned int head, unsigned int position)
 {
-	// every other track is missing
-	if(position&1)
+	// every other track is missing, as is any head above 0
+	if(position&1 || head)
 		return std::shared_ptr<Track>();
 
 	// figure out where this track starts on the disk
diff --git a/Storage/Disk/Formats/D64.hpp b/Storage/Disk/Formats/D64.hpp
index 93c4d4cb5..7b3b20291 100644
--- a/Storage/Disk/Formats/D64.hpp
+++ b/Storage/Disk/Formats/D64.hpp
@@ -35,7 +35,7 @@ class D64: public Disk {
 
 		// implemented to satisfy @c Disk
 		unsigned int get_head_position_count();
-		std::shared_ptr<Track> get_track_at_position(unsigned int position);
+		std::shared_ptr<Track> get_track_at_position(unsigned int head, unsigned int position);
 
 	private:
 		FILE *_file;
diff --git a/Storage/Disk/Formats/G64.cpp b/Storage/Disk/Formats/G64.cpp
index 920ac856f..86df3022f 100644
--- a/Storage/Disk/Formats/G64.cpp
+++ b/Storage/Disk/Formats/G64.cpp
@@ -54,13 +54,14 @@ unsigned int G64::get_head_position_count()
 	return _number_of_tracks > 84 ? _number_of_tracks : 84;
 }
 
-std::shared_ptr<Track> G64::get_track_at_position(unsigned int position)
+std::shared_ptr<Track> G64::get_track_at_position(unsigned int head, unsigned int position)
 {
 	std::shared_ptr<Track> resulting_track;
 
 	// if there's definitely no track here, return the empty track
 	// (TODO: should be supplying one with an index hole?)
 	if(position >= _number_of_tracks) return resulting_track;
+	if(head >= 1) return resulting_track;
 
 	// seek to this track's entry in the track table
 	fseek(_file, (long)((position * 4) + 0xc), SEEK_SET);
diff --git a/Storage/Disk/Formats/G64.hpp b/Storage/Disk/Formats/G64.hpp
index 82ab9ae97..35db52efb 100644
--- a/Storage/Disk/Formats/G64.hpp
+++ b/Storage/Disk/Formats/G64.hpp
@@ -37,7 +37,7 @@ class G64: public Disk {
 
 		// implemented to satisfy @c Disk
 		unsigned int get_head_position_count();
-		std::shared_ptr<Track> get_track_at_position(unsigned int position);
+		std::shared_ptr<Track> get_track_at_position(unsigned int head, unsigned int position);
 
 	private:
 		FILE *_file;
diff --git a/Storage/Disk/Formats/SSD.cpp b/Storage/Disk/Formats/SSD.cpp
new file mode 100644
index 000000000..490d5ce9d
--- /dev/null
+++ b/Storage/Disk/Formats/SSD.cpp
@@ -0,0 +1,51 @@
+//
+//  SSD.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 18/09/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#include "SSD.hpp"
+
+#include <sys/stat.h>
+
+using namespace Storage::Disk;
+
+SSD::SSD(const char *file_name) : _file(nullptr)
+{
+	struct stat file_stats;
+	stat(file_name, &file_stats);
+
+	// very loose validation: the file needs to be a multiple of 256 bytes
+	// and not ungainly large
+
+	if(file_stats.st_size & 255) throw ErrorNotSSD;
+	if(file_stats.st_size < 512) throw ErrorNotSSD;
+	if(file_stats.st_size > 800*256) throw ErrorNotSSD;
+
+	_file = fopen(file_name, "rb");
+
+	if(!_file) throw ErrorCantOpen;
+}
+
+SSD::~SSD()
+{
+	if(_file) fclose(_file);
+}
+
+unsigned int SSD::get_head_position_count()
+{
+	return 1;
+}
+
+unsigned int SSD::get_head_count()
+{
+	return 1;
+}
+
+std::shared_ptr<Track> SSD::get_track_at_position(unsigned int head, unsigned int position)
+{
+	std::shared_ptr<Track> track;
+	return track;
+}
diff --git a/Storage/Disk/Formats/SSD.hpp b/Storage/Disk/Formats/SSD.hpp
new file mode 100644
index 000000000..a45a21721
--- /dev/null
+++ b/Storage/Disk/Formats/SSD.hpp
@@ -0,0 +1,48 @@
+//
+//  SSD.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 18/09/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#ifndef SSD_hpp
+#define SSD_hpp
+
+#include "../Disk.hpp"
+
+namespace Storage {
+namespace Disk {
+
+/*!
+	Provies a @c Disk containing a DSD or SSD disk image — a decoded sector dump of an Acorn DFS disk.
+*/
+class SSD: public Disk {
+	public:
+		/*!
+			Construct a @c D64 containing content from the file with name @c file_name.
+
+			@throws ErrorCantOpen if this file can't be opened.
+			@throws ErrorNotD64 if the file doesn't appear to contain a .D64 format image.
+		*/
+		SSD(const char *file_name);
+		~SSD();
+
+		enum {
+			ErrorCantOpen,
+			ErrorNotSSD,
+		};
+
+		// implemented to satisfy @c Disk
+		unsigned int get_head_position_count();
+		unsigned int get_head_count();
+		std::shared_ptr<Track> get_track_at_position(unsigned int head, unsigned int position);
+
+	private:
+		FILE *_file;
+};
+
+}
+}
+
+#endif /* SSD_hpp */