You think Vogons will NOT build and want a new, even more obscure sound card? 😀

At this point I would put SMS VDP (mini-DIP64 or ZIP64) in the mix too or maybe the MD VDP (QFP128), to have the right PSG (TI chip is not fully compatible !).

I seond that. Also add a Z80, please (any formfactor you like; if you can. It also could be an optional circuit part the card doesn't need to function)!
That would make the card a co-processor board for both retro music and retro programming (the Z80 was MD's audio processor)! 😁

Z80 with dualported memory 😁 so memory can be written from PC and Z80.

We probably need to add an MC68k and have the whole thing on ISA slot... ahh, what the heck, who needs that ISA slot?? 😁

SMS VDP should definitely go there, even if the video part remains unused. TI PSG has differences that will be audible in many SMS games and some MD games and some of it cannot be corrected in software.

You could probably work IBM Music Feature Card compatibility into this. The sound chip is similar, you just need to replicate the interface. Scali has put a lot of effort into figuring it out; hope he sees this thread.

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.

Tiido wrote:

SMS VDP should definitely go there, even if the video part remains unused. TI PSG has differences that will be audible in many SMS games and some MD games and some of it cannot be corrected in software.

But are these available anywhere? A quick search for 315-series gave no results.

xjas wrote:

You could probably work IBM Music Feature Card compatibility into this. The sound chip is similar, you just need to replicate the interface. Scali has put a lot of effort into figuring it out; hope he sees this thread.

If I'm not mistaken, IMFC uses YM2164, that is 8-voice and YM2151-compatible, but YM2612 is 6-voice, so it will not give full compatibility. Anyway adding YM2151 to the card is not a big deal - we already have VDP and Z80 with dual-port memory onboard, so why not 😵

Concerning Z80, there is no need in dual-port memory, as Z80 has /BUSREQ and /BUSACK lines, so it can share its memory with ISA bus easily, a 64k SRAM chip will be enough.
Cannot imagine yet where it leads to with all that stuff onboard. I get Tiido's concerns about genuine sound reproduction, but Z80? VDP + Z80 - a full-fledged hardware ISA-accessed Sega Master System with an YM2612.. and maybe YM2151? 😳

A little bit offtop, but anyway, these are photos of a modular Z80 computer I made 2 years ago, its bootloader is in ROM, the shell boots from USB flash, communication via USB serial (FT245RL chip) and it has a minimal OPL2 module (leftmost bottom row) and can play IMF files 😀

Aliexpress and utsource returned some results on 315-5246 (SMS2 VDP), kinda expensive though.

MD VDP and its clones are plentiful (315-5313, SE-95, TA-06 etc.) from various sources but these are QFP128 rather than some through hole part.

I'm also making a small CPLD clone but it needs two EPM7128SLC84 parts (bigass chips 🤣) and i haven't yet tested things.

http://www.z80.info/zip/z80isacard.zip

i found this some years ago, but never found the energy to give it a try 😀

ok yet it looks like you're going to build a hardware assisted emulation platform.

Hey, thanks for the link. Looks interesting. 😁
I was thinking more of a single-board computer design like the EMUF, though. 😅

Source: https://de.wikipedia.org/wiki/EMUF

Source: http://retro-compi.feste-ip.net:37850/index.p … r/z80-mini-emuf

Anyway, it was just an idea. No reason to clutter the sound card because of that.

Tiido wrote:

Aliexpress and utsource returned some results on 315-5246 (SMS2 VDP), kinda expensive though.

MD VDP and its clones are plentiful (315-5313, SE-95, TA-06 etc.) from various sources but these are QFP128 rather than some through hole part.

I'm also making a small CPLD clone but it needs two EPM7128SLC84 parts (bigass chips 🤣) and i haven't yet tested things.

Cpld sounds promising, 2 chips for the whole thing? Or just a PSG part?

2 chips just for PSG, one chip generates the squarewaves and noise, other applies volume and converts it to i2s stream for a standard DAC. GameGear stereo support is also a design goal.

Speaking of the Genesis/Megadrive sound system, are there any plans yet to replicate the sound (in style) of its weird mono audio amp ?
You know, the one that causes the deep "full" & bassy sound (in comparison to thin stereo out via headphones jack). 😀

Tiido wrote:

2 chips just for PSG, one chip generates the squarewaves and noise, other applies volume and converts it to i2s stream for a standard DAC. GameGear stereo support is also a design goal.

2x 84-pin PLCCs for a PSG? But can it be optimized to at least 1.. 68pin? 😀

Jo22 wrote:

Speaking of the Genesis/Megadrive sound system, are there any plans yet to replicate the sound (in style) of its weird mono audio amp ?
You know, the one that causes the deep "full" & bassy sound (in comparison to thin stereo out via headphones jack). 😀

Thanks for the tip! It uses LM358 to mix L and R signals with gain of 3, but there is also a buffer inside CXA1145 which maybe does the trick you are talking about. Anyway I need to replicate the original output path without CXA and see what happens.

There's no EPM7256SLC84 so no, two chips are needed, all the 256MC chips are in very large packages like SQP208. There's too much storage needed to put into single chip along with the logic. Most/all of the glue logic should fit into the CPLDs in addition to PSG though.

Awaits the existence, followed by a Sakimoto/Follin FM driver for everything

Tiido wrote:

There's no EPM7256SLC84 so no, two chips are needed, all the 256MC chips are in very large packages like SQP208. There's too much storage needed to put into single chip along with the logic. Most/all of the glue logic should fit into the CPLDs in addition to PSG though.

But what are these differences between TI PSG and sega implementation?