One of the selling points used to position the Coupé in the marketplace (which is often debated as both a good or bad move on the part of MGT) was as the upgrade to the ZX Spectrum and thus you could play backwardly compatible speccy games whilst enjoying the new features of the machine.
This meant that MGT had to provide some form of emulation to ship with the machine to allow this and was supplied with the machine in the MGT Utility Tapes.
What users were not told at this stage was that the emulation was for the 48K only and not the 128K machines, in fact emulation of the 128K’s memory map would prove impossible at workable speeds. Simon Cooke began work on an emulator that ran at best at about 1/16th of the required speed although many demos and games were converted manually to great effect by people like Simon Cooke, Stefan Drissen and Edwin Blink.
The original emulation was via a 'skeleton' ROM image (not containing any copyrighted code) that was not 100% compatible leading to many problems with software that made extensive ROM routine calls or utilised undocumented calls or features.
Another issue discovered was that getting the software to load at all was an often problematic due to subtle differences in machine timing.
Many games with anti-piracy software protection loaders that used tight timing like Speedlok and Hyperload would not work at all.
To address this MGT quickly engaged the services of Graham Mason a well known hacker on the Speccy scene and Your Sinclair’s resident ‘game cheats’ expert to provide workarounds for the loaders. This was written in January 1990 and distributed with the SAMDOS boot disk and with the ROM upgrade.
Users soon found that by aquiring a copy of the Spectrum 48K ROM with a few minor POKE adjustments gave much better emulation results and lists of ‘compatible’ titles started appearing in magazines such as Fred and even some games listed themselves as SAM Coupé Compatible like Thalamus’s Delta Charge.
Some ‘standard hacks’ to make the ROM operate originally from Format (Vol 3 Issue 5 January 1990) by Ken Elston appeared in many publications including Fred 1 as well as instructions for replacing the ‘skelt.bin’ ROM image from the MGT emulator.
A market then grew for 3rd party Spectrum emulators that offered enhanced features such as superior file handling, correct keyboard mapping and even fixes to the timing bugs introduced by running on the Coupé and thus allowing games to load without the need for the loader hacks.
Many such emulators were produced with titles like LERM Software’s SamTape, SC_Speclone and Specmaker leading the pack.
In 1991 SamCo released a hardware solution for transferring data called The Messenger that could send snapshots from the Spectrum after they had loaded, the only disadvantage was that you had to have the Spectrum hardware.
In 1999 as part of B-DOS development work a hard disk patched ZX Spectrum 48K emulator was released by Martijn Groen with support for Sam 48K files, SNA, Z80, SP, TAP, SamTape and even the Triple Joystick Interface.
More recently velesoft has developed an emulator called Snaper which allows you to run ZX Spectrum 48k and 128k software using the external One Meg interface.