Voodoo 2 Total Memory Size?

[walterg74]

Hi all,

I'm confused with the memory settings for the Voodoo 2 card emulation, specifically on how to emulate a 12MB card.

I know it's there as it's even in the readme stating:

3DFX Voodoo 2: PCem can emulate both 8 and 12 MB configurations.

But I'm surely missing how to configure it...

I found an old post (that's I didn't wanna necro) where leilei states to a user:

"It's already there.

Voodoo2 8mb = 4mb framebuffer, 2mb texture memory * 2 texture mapping units
Voodoo2 12mb = 4mb framebuffer, 4mb texture memory * 2 texture mapping units "


So, first my confusion is... Don't ALL Voodoo 2 cards have 2 TMUs, with 8MB cards having 4MB Framebuffer, 4MB Texture Mem and 2 TMU chips and 12MB cards having 4MB framebuffer, 8MB Texture Mem and the same 2 TMU chips..?

Even if that's wrong, etc. etc. and I follow the indications above, is it just setting the memory as above to 4/4 and that's it? Like is it because PCem treats that number as "Texture Memory at the disposal of each TMU" and not as the total physical memory installed as in real life..?

[omarsis81]

So, first my confusion is... Don't ALL Voodoo 2 cards have 2 TMUs, with 8MB cards having 4MB Framebuffer, 4MB Texture Mem and 2 TMU chips and 12MB cards having 4MB framebuffer, 8MB Texture Mem and the same 2 TMU chips..?

I can't see where your confusion is. Indeed all Voodoos2 have 2 TMUs regardless the memory size they have. Some have 8 and other 12mb. What's wrong with that?

[omarsis81]

What I DO see troubling to me is that 8mb and 12 mb both have fixed 4MB frame buffer memory (at least the Monster, Creative and all known brands). So why bother with playing with the frame buffer memory from 4 or 2mb?

[leilei]

The option's there for curiosity (a 2mb framebuffer Voodoo2 would've been for arcade machines)

A Voodoo2 always have two TMUs, and that chosen texture memory will be multiplied by 2 always on the Voodoo2 option. Same goes for the Obsidian SB50 above it. Consumer V2s always had a 4MB framebuffer, and either 4mb or 8mb of total texture memory (the second half reserved for the second TMU typiclaly in use for multitexturing)

[walterg74]

The option's there for curiosity (a 2mb framebuffer Voodoo2 would've been for arcade machines)

A Voodoo2 always have two TMUs, and that chosen texture memory will be multiplied by 2 always on the Voodoo2 option. Same goes for the Obsidian SB50 above it. Consumer V2s always had a 4MB framebuffer, and either 4mb or 8mb of total texture memory (the second half reserved for the second TMU typiclaly in use for multitexturing)

Right, so it's probably just me being slow, but the confusion stems from the implicit "this will be multipied by 2 cause there's 2 TMUs" instead if having the "texture memory" field reflect the total amount of memory for it. (And same not applying to voodoo 1, because of implicitness)

[leilei]

Just know there's many older games that don't understand multitexturing/second TMUs and effectively use the V2 as if it were a 4-6MB Voodoo1 card.

The number is also consistent with driver's control panel itself. There's a checkbox to restrict the texture memory to 2MB (for the 4MB tmem models) to regain some older Glide game compatibility, and would function like a "Voodoo2 8mb"