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Voodoo 3 snow/glitches and AGP vs PCI BIOS questions

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First post, by darry

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I just flashed my PCI Voodoo 3 3000 to Powercolor's 2.15.12-SD BIOS (the original version, not the one with relaxed memory timings; see below for details ) whereas it initially had BIOS 2.15.06-SD .

I have no idea whether the 2.15.12-SD BIOS was taken from the PCI or AGP version of the card (it came from http://3dfxbios.stantoworld.co.uk/ ).

The reason I did the flash was to resolve issues with snow/horizontal glitches in certain 2D modes, for example, in Impulse Tracker and in Quake's 320x200 VESA mode only (higher resolution were OK in Quake). The issue is similar to the "snow" described in Voodoo3, shaky picture and snow .

The BIOS upgrade seems to have fixed the issue 100% for me . What seems curious to me is that it took that specific BIOS to fix the issue . Downclocking to 143 MHz with the original BIOS did nothing and neither did the modified2.15.12-SD with relaxed memory timings .

Questions :
Are PCI and AGP Voodoo 3 BIOS ROMs supposed to be interchangeable ?
Anybody have an idea as to why this BIOS version, with reputedly more aggressive memory timings, fixed the issue ?

Reply 1 of 1, by darry

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According to this thread, 3DFX Voodoo 3 3000 - Inconsistencies with some DOS and Windows Games , the snow can be caused by write combining being enabled. I actually do use fastvid regularly, but it does not seem to cause any snow since the updated Voodoo 3 BIOS . Prior to the update, I had the issue whether or not fastvid was used .

The machine is Tualatin-S @ 1400MHz whose BIOS does not seem to have any option to enable or disable write combining as far as I can tell. Additionally, the fact that fastvid increases performance leads me to believe write combining is not enabled by default .

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