ZX Spectrum hardware emulation on MSX

By mceiras

Supporter (4)

mceiras's picture

24-01-2019, 17:51

Would be possible natively run zx-spectrum games on MSX with the FPGA-synthesized ULA in a cartridge in the same way that franky / Playsoniq does natively running Sega Master System games on MSX?

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By Pencioner

Scribe (1508)

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24-01-2019, 18:04

Screen can be emulated technically (looks like memory mapped i/o device would serve that purpose nicely, mapped to 4000h address) but i bet some software which relies on exact timing for graphic effects (demos and some games) will not run correctly due to extra M1 wait in MSX

By TomH

Champion (327)

TomH's picture

24-01-2019, 19:16

I would dare imagine IO collision would be a problem too?

The Spectrum idiomatically uses port FE for ULA access (which includes keyboard reading and 48kb sound output) but will accept any even address. Even well-behaved software that uses FE would surely trip over the MSX 8000-BFFF paging register? And there are bound to be games and demos that use some other even port with the expectation that the ULA will be there.

There's also a small handful of titles that read an undefined port to spy on the last fetched byte of video data. Everybody always cites Arkanoid. It's a really, really small handful though. I'm not sure that even works on a 128kb Spectrum.