Quake 3 is a good example. Voodoo 2 SLI has various stuttering due to lack of texture memory, while a V3 works a lot better.

Quake3's good yes. The starting point in Deva Station works too well for that as it immediately presents you over a grate with a portal underneath. Note that the SLI just doubles the thrashing penalty that a single V2 would get in the same areas. "24MB VRAM" means diddly squat here. Even a Banshee will kick V2SLI's ass there.

Another texture heavy game on the same idtech (for newer cards in mind) is either 2002 Raven game - Soldier of Fortune 2 and Jedi Knight 2:Jedi Outcast. For CD games, they're LOADED with 1024x1024 textures, so good luck with r_textureBits 32, r_picmip 0 and r_ext_compress_textures 0!

I think I ran into a texture memory issue in Fallout 3 several years ago.

I was trying to benchmark the game on some late AGP cards by running around in a predetermined path.
With a 7600GS AGP card with 256MB, the game would stutter and struggle for a while, and then either crash, or start running smoothly. If it survived this, then it would keep running fine after that. My guess was that it was texture swapping and sometimes failed to get itself settled to a stable condition.
With a Radeon HD2600XT 512MB card, the game ran without any of that drama.
I'm sure graphics settings have a bearing on this though. I don't think I ran it any lower than "Medium" because the menus were such a blurry mess on "Low" I didn't consider it usable.

Kahenraz wrote on 2022-04-01, 07:30:

I think this will only be applicable to AGP cards, through the use of AGP texturing to use system memory when there isn't enough dedicated memory available.

AGP texturing was never viable, take an Intel AGP poster boy https://vintage3d.org/i740.php barely scrapping bottom of the 3D market when released

Depending on how it's used, I still see it as a useful technology. It allows assets to be loaded from disk into fast system memory and copied into even faster video memory as needed. The alternative would be to read from disk in demand. And, realistically, this was not actually a viable alternative ever.

It may not have been fast, but it did at the very least bring some form of equitable memory capacity for everyone simply by them buying an AGP card. Not every game needed instant access to video memory, and AGP texturing allowed the use of much larger texture maps where it would otherwise have been impossible.

Kahenraz wrote on 2022-04-05, 07:25:

Depending on how it's used, I still see it as a useful technology. It allows assets to be loaded from disk into fast system memory and copied into even faster video memory as needed. The alternative would be to read from disk in demand. And, realistically, this was not actually a viable alternative ever.

I've never worked with AGP on any technical level so I might be misunderstanding the feature, but I think the difference must simply be one of DMA versus requiring the CPU to perform the transfer. There shouldn't be anything stopping the programmer from caching textures in RAM, but then it would be up to the program (or more realistically the video card driver) to do the reads and writes instead of the video card being able to do them directly. This of course ties up the CPU.
I remember seeing an option in NVidia drivers for how much RAM to use for caching with PCI cards, so I think that must be emulating AGP functionality at the driver level.

Presumably with (true) AGP the CPU can continue running other instructions while a DMA transfer is happening between the RAM and video card - which is fine up until the CPU experiences a cache miss. At that point it would still have to wait since the memory bus is tied up by the AGP transfer.

AGP texturing is not transferring textures from main ram to gpu ram when needed, AGP texturing is TMU units directly making texture lookups from main memory thru AGP slot. There was no MMU on the GPU at that time, this was not the case of virtual GPU memory pool swapping to main ram after exhausting local ram.

Just to drive this home: good old PCI Voodoo2 has 720 MB/s dedicated to each of its TMUs, 1.4 GB/s total just for texture units. Banshee 1.6 GB/s, TNT 1.7 GB/s
AGP x2 is 533 MB/s 😀 You know whats in this ballpark? Voodoo1 with dedicated 400 MB/s TMU bandwidth. This is reflected in the benchmarks: https://web.archive.org/web/20220331012644/ht … /3dfx/bench.htm