LABS wrote:We probably need to add an MC68k and have the whole thing on ISA slot... ahh, what the heck, who needs that ISA slot?? 😁
matze79 wrote:Z80 with dualported memory 😁 so memory can be written from PC and Z80.
Haha, yeah, I think the same! 😁 But really, a basic Z80 system is easy to make (nowadays). The AX81 project managed to emulate a ZX81 - Z80 + custom chips within a single Atmel chip.
For a CP/M computer, a SIO, PIO and some RAM (64K or less) would be required (+boot medium). No extra RAM refreshing necessary, the Z80 has it built-in.
So I believe, a simple Z80-on-a-bus design could be built which much less. It even could get its boot code from the ISA bus, if appropriate address range mapping was used.
The reason why I vote for a little Z80 is - the audio engines of the Genesis and Mastersystem games were written for the Z80, sure sometimes in parts only (using 68K code, too).
Having a little Z80 or compatible chip on the card, it could be in SMD even, would provide an interesting platform for (retro) thinkering.
Some could modifiy one of these old CP/M emulators to take advantage of that, or run old arcade games on it (in parts, many used the 8080/8085/Z80 line).
Anyway, it's just an idea. 😀 Making a full-blown Z80 board is overkill, it's a sound card project, after all and I don't mean to change this.
Just thought it would be cool to add a Z80 that -if feasible- would be accessible on the PC side, too. 😎
Maybe by using ports, via an on-board serial port (RS232 to Z80 SIO) or by creating mapped memory.
(An 64K block in UMA which both PC and Z80 could address/share, for example. Perhaps by using that dual-ported RAM..)
That being said, I'm no engineer. What I mean is akin to the Z80 Softcard for the Apple II.
Or this board: https://youtu.be/SbYcjrezJHs?t=112
Wait, don't get a heart attack yet, It's that big because of being so old (early 80s). 😁
The original Hercules card was huge, too, but later clones only had a handful of parts installed.
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