Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Discussion about old sound cards, MIDI devices and sound related accessories.

Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby bjwil1991 » 2019-11-04 @ 16:35

I do not get any graphical glitches with the PC Speaker at all. I only have a 486 machine, no less. I did not run the TSR software yet as I need to look for my external IBM FDD for my ThinkPad R40 to write to diskettes. Maybe I'm missing something, and I do disable the cache on the CPU and might find an L2 cache control software to slow the system down a bit more and see what happens.
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby Benedikt » 2019-11-04 @ 17:41

Erm...
If you are not using the TSR, doesn't that mean that the Tandy audio output routines will write to the default port and mess up the secondary DMA controller which might then write garbage to random memory locations?
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby Scali » 2019-11-04 @ 18:00

Benedikt wrote:If you are not using the TSR, doesn't that mean that the Tandy audio output routines will write to the default port and mess up the secondary DMA controller which might then write garbage to random memory locations?


That is an interesting theory.
It would explain why only certain games have the problem:
The secondary DMA controller would have to be initialized in a certain way for the data to actually end up on screen. So only games that use the secondary DMA controller in a certain way will have the issue.
In other cases you may still be randomly writing data to memory, you just won't see it :)

I think this may have to be investigated further.
If your theory is true, then the same problem should occur on every machine with a secondary DMA controller. And it should never occur on a machine without one.
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby bjwil1991 » 2019-11-04 @ 18:02

I will download the TSR and push it to my 486 by connecting my IBM laptop running XP to the network card and see what happens.
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby Benedikt » 2019-11-04 @ 18:20

Scali wrote:That is an interesting theory.
It would explain why only certain games have the problem:
The secondary DMA controller would have to be initialized in a certain way for the data to actually end up on screen. So only games that use the secondary DMA controller in a certain way will have the issue.
In other cases you may still be randomly writing data to memory, you just won't see it

It was just a wild guess, but maybe some games use the second DMA controller to move large chunks of graphics data around on screen.
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby bjwil1991 » 2019-11-07 @ 00:11

I noticed a bit of a graphical glitch with the PC Speaker. Maybe the game has a bug in it. The Tandy TSR runs only with the EMM386 and HIMEM disabled. Getting somewhere.
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby derSammler » 2019-11-07 @ 12:08

Benedikt wrote:It was just a wild guess, but maybe some games use the second DMA controller to move large chunks of graphics data around on screen.

Nice idea, but that's not how DMA works.
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby bjwil1991 » 2019-11-07 @ 12:49

Funny thing is, King's Quest 1 and 3 EGA, Space Quest 1 and 2 EGA, and Police Quest 1 and 2 EGA work fine with the Lo-Tech Tandy sound card. I discovered that King's Quest 2 had graphical glitches when using a card newer than EGA, such as VGA. Works in DOSBox and I like using real hardware for games, so...
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby Benedikt » 2019-11-07 @ 16:41

derSammler wrote:
Benedikt wrote:It was just a wild guess, but maybe some games use the second DMA controller to move large chunks of graphics data around on screen.

Nice idea, but that's not how DMA works.

Some architectures can use their DMA controllers for memory-to-memory transfers. But you're right: The 8237 and friends can't do that. I forgot about that.
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby Scali » 2019-11-07 @ 21:33

Benedikt wrote:Some architectures can use their DMA controllers for memory-to-memory transfers. But you're right: The 8237 and friends can't do that. I forgot about that.


No, but you could still have corrupted graphics because of broken DMA transfers, if DMA is used to read the graphics from disk into memory.
Mind you, it's rare that HDD controllers use the 8237 for that. The ones that do are generally 8-bit cards, so that would rule out 16-bit transfers. But who knows :)

And theoretically you can use the 8237 for memory-to-memory transfers. It's just... limited, because it only has 16-bit addressing.
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby matze79 » 2019-11-09 @ 10:20

Hm i have no issues with KQ2 on XT, works perfect.

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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby matze79 » 2019-11-10 @ 12:08

Ordered new PCBs :)
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby root42 » 2019-12-10 @ 12:17

My card got modded by matze and works perfectly now. Less noise, thanks to better power supply, and no graphical glitches anymore when using the Tseng ET4000:

https://youtu.be/j5_xFX0AFN0

https://youtu.be/l0CszeCVc8A
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Re: Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

Postby matze79 » 2019-12-13 @ 14:05

glad it works, i already recieved some revised pcbs but they have dead via`s so i have to reorder.
but good thing is i got my money back.

smd version first.. dht version will follow later :)

already shipped but i`m still waiting for china post :D
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