I may have written the first ZX Spectrum emulator, for some definition of emulator.
In the 80s I had a BBC Micro with a Z80 second processor attached to its "tube" bus. Usually the Z80 ran CPN, a business operating system similar to CP/M with its own flavour of BBC Basic, including a built-in Z80 assembler. But it could be asked to do anything.
Some Spectrum software ran ok on the Z80 if you could get the memory image loaded, which I eventually did. The 6502 wasn't fast enough to provide good emulation, but it could poll the Z80 memory and convert the video image to something the BBC side could display. With some clever tricks the BBC's ULA could even be persuaded to simulate Spectrum square pixel resolution with most of the colours, and I used rapidly flashing colours to get more.
It wasn't good enough to run games, though it could show some of the screens.
But I remember it successfully playing one of the best Spectrum music demos of the time, because the 6502 was fast enough to poll and relay the 1-bit audio signal being generated by the Z80 music software.
In the 80s I had a BBC Micro with a Z80 second processor attached to its "tube" bus. Usually the Z80 ran CPN, a business operating system similar to CP/M with its own flavour of BBC Basic, including a built-in Z80 assembler. But it could be asked to do anything.
Some Spectrum software ran ok on the Z80 if you could get the memory image loaded, which I eventually did. The 6502 wasn't fast enough to provide good emulation, but it could poll the Z80 memory and convert the video image to something the BBC side could display. With some clever tricks the BBC's ULA could even be persuaded to simulate Spectrum square pixel resolution with most of the colours, and I used rapidly flashing colours to get more.
It wasn't good enough to run games, though it could show some of the screens.
But I remember it successfully playing one of the best Spectrum music demos of the time, because the 6502 was fast enough to poll and relay the 1-bit audio signal being generated by the Z80 music software.