What is the goal with this design? From the recent image, I can see that there is an OPL4 with flash, presumably for instrument data. Will you be exposing the OPL4 directly at all, or only as an MPU-401 device via the YMZ290? Are you planning to use the FM portion at all? Is the CPLD just for bus logic and glue, or other tasks as well?

On the software side, are you planning to try re-using the SW20 TSR, writing your own, or doing MPU-401 in your firmware?

I don't know what you're planning with this, but it is already starting to look interesting.

This card is to create a solution to my YMF721 issue first and poremost. The primary goal is to make a MIDI synth with the ARM MCU and secondary goals are to do intelligent MPU-401 and Sound Blaster emulation.

As far as OPL4 goes, I had several YMF278 chips and I really liked SW20PC MIDI but that card is incredibly speed sensitive so I lifted the MIDI section and put it on this card. I don't have plans to do anything with the OPL4 outside what Yamaha already planned and this will not appear in any new cards either that I'll make either. There's also the sample ROM issue if it was gonna become something I would intend to sell, there's nothing that can be legally distributed and I have no intentions of making my own set. This card is solely for development and some personal fun 🤣.

Tiido wrote:

The primary goal is to make a MIDI synth with the ARM MCU and secondary goals are to do intelligent MPU-401 and Sound Blaster emulation.

Have you figured out what you'll use for instrument data with this? If not your own set, and if you're not basing the design on the YRW801, is there another plan?

YRW801 is possible but custom TSR is then needed (or maybe some YRW801 using card's software can be used/adapted), I'll use SW20PC ROM instead (for YMF278). Actually another design goal is to work out some effect processing things with the ARM, I am running the output of YMF278 into the ARM for DSP action and there's a dedicated DAC for the ARM too. I won't be replicating functonality of Yamaha's effect processors but going full custom stuff. It is gonna be quite fun little thing, paving way for a few future projects ~

ARM synth uses actual synthesis based on Phase Modulation and few other methods, there will be very few samples used (primarly percussion).

Tiido wrote:

YRW801 is possible but custom TSR is then needed (or maybe some YRW801 using card's software can be used/adapted), I'll use SW20PC ROM instead (for YMF278).

I wasn't aware that the ROM on the SW20-PC was substantially different from the YRW801; I thought it was just a different revision without the YRW numbering. Do you prefer the sound of that ROM over the YRW801?

It sounds mostly like the softsynth of last YMF71x drivers so I definitely very much prefer it. There's more sounds and several drumkits rather than just one aswell. The DOS TSR only ever uses single kit and doesn't do anything fancy though and probably sounds quite like YRW801 using hardware, but Windows driver uses all the sounds available and can also mix in FM when polyphony is getting too high, with pretty nice results.
Something I made a while ago with the SW20PC (with my very own reverb "algo" no less 🤣) : https://soundcloud.com/tiido/sleepy-yamaha

First setback, the CPLD actually cannot hold the design I had in mind in its entirety. While data can go into all parts of the CPLD without any major limitations, it cannot really come out of it without using lot of resources and I have two bidirectional buses, I can pretty much only handle one of them with one chip. So the solution is I just piggyback another CPLD on top of the old, each doing half the work 🤣. Praise JTAG chain ! hahaha

very nice sleepy tune!
I wish OPL4 was used better in PC world... I bought the SW20-PC back when it was new and still have it boxed 😀 one of the few things I kept from back then 😀

OPL4 lacked one major thing : DRAM support. If it had that it could have went heads of with GUS (and AWE32). Later flavor of OPL4 called OPL4D did have DRAM support but it came too late to make any difference.

The original YMF278B did have support for using a portion of its address space for SRAM. The usual 2 MiB ROM configuration left room for up to 2 MiB SRAM, still more than the GF1 offered at the time.

The OPL4-D was supposed to support DRAM, but I have never read of any PC cards using the YMF295, nor am I aware of it ever having become a shipping product.

In the PC world, sound cards with RAM were never used to their full advantage, since it was an uncommon feature. With years of the GUS in its various forms, the AWE line from Creative and a few OPL4 boards with SRAM expansion options, the number of major titles that used custom samples or effects is still rather small. Later, even DLS never saw much use. It's an unfortunate reality; we could have enjoyed much better audio otherwise.

Didn't the SW20-PC have 128kb of sram to load custom samples? Pretty sure it did?
Also there are several MSX+OPL4 videos on yt with impressive tunes, do these use extra ram?

With 512KB SRAM, I find the OPL4 sample playback to compare pretty favorably to that of the GUS and AWE32:

http://www.symphoniae.com/soundcard/MediaTriX … OPL4_GUITAR.mp3
http://www.symphoniae.com/soundcard/MediaTriX … SPACEDEBRIS.mp3
http://www.symphoniae.com/soundcard/MediaTriX … ELCHAMBERS2.mp3

But where we're talking about a $500+ soundcard in 1994 (w/expansions), ~$100 of which is the SRAM alone, it was something of a marketplace non-starter. I think this may be what Tiido is referring to.

keropi wrote:

Didn't the SW20-PC have 128kb of sram to load custom samples? Pretty sure it did?

That it does.

There's 128KB (optional according to manual) on SW20PC. SRAM is super expensive companed to DRAM, probably the 128KB on SW20PC cost as much as 512KB of DRAM on other cards...

MSX expansions came with lot of SRAM by standard to allow SFX and whatnot in games, the CPU is incapable of doing software mixing and a serious game at the same time unlike PCs.

There can be 4MBytes of memory if you wanted, the !WE signal is active in the entire address space. The different configurations are only to facilitate use without need for external address decoder for the memory chips, in fact SW20PC doesn't even use the "SRAM mode" on it.

I haven't seen OPL4D anywhere either but some sort of articles I found seemed to suggest it did see light of day and even buying price was listed.

I guess the need to support vanilla SB is the reason things never took off on that regard, even if OPL4 chips were roughly 20usd and shouldn't have been a problem to add to any card willing...

mine came with the sram pre-installed I don't think there are versions without it
anyways one flaw of the card is the "MAD16" chipset that provides sb support, it was and is crap IMHO
I remember having issues with some games, some had to be in SB mode, others in SBPRO, others just force them to use SB....
I had no idea those msx carts had extra ram , good to know

The early MAD16 used on the card is garbage indeed, I never got any consistent results with it in games and when there's sound it is only mono... Later ones are much better.

can they be swapped?

There's no pin compatible version out there so any swapping becomes essentially redoing half the card. Plus the way effect processor is controlled is completely tied to how the MAD16 works. It is also part of the reason why the card is speed sensitive and won't work in all hardware.

I see... well it is what it is 😁

keropi wrote:

Also there are several MSX+OPL4 videos on yt with impressive tunes, do these use extra ram?

My understanding is that those are almost all a combination of YRW801 ROM-based instruments supplemented with a few extras loaded into the SRAM. The limitation is that there are several versions of the cartridge, with varying amounts of SRAM.

Cloudschatze wrote:

But where we're talking about a $500+ soundcard in 1994 (w/expansions), ~$100 of which is the SRAM alone, it was something of a marketplace non-starter.

Ah yes, the Audiotrix Pro. It was probably the shining example of what an OPL4 card could be; PC Magazine even put its digital audio quality in the same class as the MultiSound and other top-range Turtle Beach cards. I think one of its biggest impediments was the price (the YRW801's complete lack of additional drum kits and optional effects module didn't help, for a card in its price range). Even in its home province, at a local chain's bankruptcy sale, the bare card was $349 (CAD). That was one of the only times I actually saw one on the shelf.

CPLD interconnect limits are hit way too hard, so it is more or less a dead end... So a kludge happens that involves a Flex 10K device. So much freedom with it haha. I'll have to make a little PCB that sits in the footprint of the CPLD sometime. Something I should have done in the beginning was to use that sort of FPGA but I really wanted to use the parts left in my stash...