Newly made Gravis Ultrasound compatible cards ... what's the degree of interest?

[shock__]

Just thinking at the moment ...

I have one of those lying in front of me ...
http://i910.photobucket.com/albums/ac30 ... g~original
Which can be made compatible to classic GUS cards according to gerwin's post here by adding 512kb of RAM in the intended solder footprint.
viewtopic.php?t=31998#p340164
Might also be possible to easily boost it to 1MB.

AM78C201 & IW78C21M1 chips can still be bought as NOS from China.

Seeing how above card is a 2 layer board, it could be produced cheaply as well (~$20).

Considering GUS cards go for quite a bit these days ($80+ last time I checked) it might be possible for one to solder one's own card for maybe $30 (assuming the custom chips don't cost an arm and a leg from china).

As usual with my projects, I'd reverse the schematic, draw an example PCB layout and produce a prototype and release the files once the design is confirmed as working (I _hate_ distributing stuff) so basically anyone with soldering experience and patience to go through acquiring all parts could build his own card.

What's you guys' and gals' opinion on that?


EDIT: development blog here: viewtopic.php?f=46&t=42431

[Scali]

The original GF1 is no longer available I take it?
AMD's InterWave is nice, but I've heard people complain about compatibility issues. Apparently the playback rate is not 100% the same, which causes problems with long samples getting out of sync.
But still, InterWave is better than no GUS at all
The GUS is by far the best soundcard for early-to-mid 90s demoscene stuff.

[shock__]

The GF1 and it's companion chip GF1D1 seem to be a lot harder to obtain and has the sample rate drop issue.
Wouldn't be a good start.

Going with the Interwave chip one could also add a SIMM-72 socket for easy 16MB RAM expansion.

[elianda]

I think some more universal approach would work out better.
An ISA card where you have some CPU or DSP with some RAM that emulates a certain soundcard by firmware.
You could set the firmware and could have a GUS, SB16 some MIDI wavetable or maybe even everything at the same time on a single card.

[carlostex]

The GF1 and it's companion chip GF1D1 seem to be a lot harder to obtain and has the sample rate drop issue.
Wouldn't be a good start.

Going with the Interwave chip one could also add a SIMM-72 socket for easy 16MB RAM expansion.

I don't know about GF1D1 but GF1 PLCC's seem to be readily available from various chinese suppliers. Eiter way i love GUS'es. I have a GUS PnP and since all the games i love work great with it i'd be interested in it. In fact i think GUS PnP's are a bit more silent than the classic and MAX Ultrasounds, probably due to simpler and more integrated circuit design.

[Marmes]

I know I am new at this, but I just reversed an amiga audio card. the prelude. 4 layers board. I coud reverse a gravis with some time

[carlostex]

I know I am new at this, but I just reversed an amiga audio card. the prelude. 4 layers board. I coud reverse a gravis with some time

Welcome to Vogons!

[Scali]

I think some more universal approach would work out better.
An ISA card where you have some CPU or DSP with some RAM that emulates a certain soundcard by firmware.
You could set the firmware and could have a GUS, SB16 some MIDI wavetable or maybe even everything at the same time on a single card.

That would be great, but probably a lot more difficult to make.
As an alternative, I'd like to offer the idea of a GUS Extreme clone. The GUS Extreme has both the GF1 and an ESS AudioDrive chip for SB/opl3-compatibility.
If you would combine the InterWave with some sort of SB-compatible chip, you'd have a single card that would cover pretty much all DOS needs.
The SB-compatible chip will run all Adlib/SB stuff, and the InterWave will do GUS, native InterWave, and MT32/Sound Canvas.
If you would add a mixer with an extra PC speaker input (like some SB's have for example), you could even route PC speaker stuff through there (or you could use that magic hack that the PAS uses, to intercept the PC speaker from the ISA bus... however they do that).
Don't forget CD-rom audio inputs

[Scali]

In fact i think GUS PnP's are a bit more silent than the classic and MAX Ultrasounds, probably due to simpler and more integrated circuit design.

That may have something to do with the board revision?
I have had some GUS MAX boards rev 1.8, and some rev 2.1. The 1.8 seemed a tad noisy, but 2.1 was quiet.
I didn't do an in-depth comparison with the GUS P&P Pro that I have, but I consider both cards extremely quiet.

[Marmes]

gf1 chips are hard or almos impossible to get I think. They were proprietary chips. AMD interwave is still available.

[keropi]

welcome Marmes!

@shock__
as always I am interested in stuff like this , especially if I get to build it myself

[Marmes]

keropi, it's good to see familiar users . I wanted to make the prelude, but I guess that there isn't much interest. A gravis would be interesting. I will copy one, as soon as I get my hands on one

[keropi]

^ heh
yeah, soundcards on the amiga are not that popular...
still this GUS clone should be great, especially if it something like the ACE that is easily coupled with a sb or similar soundcard...

[shock__]

Hehe ... funnily enough my first clone project was a 4-layer amiga/atari st/mac se board as well

But yeah, personally I'd prefer a minimal GUS approach as well. SB cards are cheap these days and ESS chips may not be easy to obtain and aren't free of issues either.

[Scali]

But yeah, personally I'd prefer a minimal GUS approach as well. SB cards are cheap these days and ESS chips may not be easy to obtain and aren't free of issues either.

Well, it doesn't have to be an ESS per se. Just something that is SB-compatible. Having both on one card is nice.

[keropi]

^ nice but complicated. IMHO everyone that will use a GUS will also want at least SB16 compatibility or some 100% SBPRO deal: basically a real SB. Something like that is not so easy , unless I am wrong here.
With an ACE-like approach you can couple it with whatever SBish card you like without the need to set exotic irq/dma channels or evern bother to find a working combo.

[Marmes]

a minimal gus approach would be ideal, but the ACE board uses gf1 and other proprietary chip. I think interwave is the way to go

[keropi]

but you can still disable all the extra sb emulation(s) , right?

[shock__]

I think so ... never had a GUS Extreme myself.

As stated ... the PCA761AW would be a nice reference design ... GUS PnP compatible, can be made GUS classic compatible by adding RAM and adding up to 4 Banks of 4MB (each) of extra memory for soundfonts shouldn't be too hard.
And I have physical access to such a card.

[idspispopd]

I think some more universal approach would work out better.
An ISA card where you have some CPU or DSP with some RAM that emulates a certain soundcard by firmware.
You could set the firmware and could have a GUS, SB16 some MIDI wavetable or maybe even everything at the same time on a single card.

That would be great, but probably a lot more difficult to make.

But then you'd only need one model so support different sound standards. I don't think it should be that difficult to build, but the programming would be a lot of work.
Maybe FPGA would be better that a CPU or DSP, but doesn't the first sound blaster just use a microcontroller for everything=

As an alternative, I'd like to offer the idea of a GUS Extreme clone. The GUS Extreme has both the GF1 and an ESS AudioDrive chip for SB/opl3-compatibility.
If you would combine the InterWave with some sort of SB-compatible chip, you'd have a single card that would cover pretty much all DOS needs.
The SB-compatible chip will run all Adlib/SB stuff, and the InterWave will do GUS, native InterWave, and MT32/Sound Canvas.

I understand the arguments against this. Most useful for mainboards with only one ISA slot.

If you would add a mixer with an extra PC speaker input (like some SB's have for example), you could even route PC speaker stuff through there (or you could use that magic hack that the PAS uses, to intercept the PC speaker from the ISA bus... however they do that).

I don't think the hack is very magical (but certainly not trivial), you only need to listen to writes to the relevant ports (0x61 keyboard controller, 0x42/0x43 PIT) and replicate the logic. Just like the Chameleon simulates the VIC-II of the C64 to generate a VGA output signal.