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Joined: Jun 2014
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I'm debugging some Glide-related code in an effort to get Savage Quest to proceed. The code is writing a special value (1<<18) to the trexInit1 register (via a write to 0xe000n320, where 0xe0000000 is the sst base).
This should cause the drawTriangle command to return the card configuration, specifically how many TMUs are present. Instead, it returns all zeroes, which is interpreted as only a single TMU, but there should always be two of them. Then Savage Quest runs out of texture memory.
I don't know how Gauntlet runs, since it probably has a similar check, unless it is overriding the results somehow.
I didn't find any explicit references to trexInit1 in the Voodoo code, so it seems that no-one checks for it.
Is it something that is easy to add? The Voodoo code is huge and I'm having trouble understanding it.

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Yeah, TEXINIT* writes are currently ignored. The Atari/Midway games probably assume a fixed configuration and so don't rely on this detection method.

It doesn't sound too tricky to add. If you get stuck perhaps you can crib from whichever version of DOSBox adapted our Voodoo code; I'd assume they'd have needed to implement it.


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Thanks, I got it done. It was easy, as you thought.
I'll submit the change soon.

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I just checked Gauntlet Legends. It is interested in the value, but it probably has a default setting in case the impossible zero is returned.
I haven't noticed if there's any performance increase now that the card responds correctly.


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