As we mentioned earlier, the VSA comes from the name “Voodoo Scalable Architecture” with the stress placed on the word “Scalable.” The “Scalable” part of the VSA architecture is in the fact that up to 32 VSA-100 chips can be linked together in “SLI” mode which divides the task of rendering and displaying the lines on your screen among the chips. We have already seen this taken advantage of with the Voodoo5 5500, which features two VSA-100 chips, and we may see its return yet again with the Voodoo5 6000, which should boast four total VSA-100 chips. However, when it comes to being “Scalable,” you’re not talking about making a low-cost product, and thus the Voodoo4 4500 leaves this part of 3dfx’s VSA unused as the card features a single CPU.
Compared to the Voodoo3, the VSA-100 adds support for 32-bit color rendering, 32-bit textures, 32/24-bit Z & W, and an 8-bit stencil buffer. Furthermore, the VSA-100 can also render two single-textured pixels per clock or one dual-textured pixel per clock. Support for 2048 x 2048 textures has now been implemented into the VSA-100, thus the VSA-100 offers essentially everything the Voodoo3 lacked.
The chip is an AGP 4X part, with support for AGP 2X, AGP 1X and PCI operating modes. In spite of this, the VSA-100 does not support AGP texturing. 3dfx still feels that AGP texturing is not truly beneficial and thus there is no reason to pursue support for it with their products. The chip itself is composed of 14 million transistors, a little more than half the count of the original GeForce, and is manufactured on an enhanced 0.25-micron, 6-layer metal process. The "enhanced" 0.25-micron process just means that it takes advantage of shorter gate lengths, which allow for faster switching, thus allowing for higher frequencies and greater yields at those frequencies.
At the launch, 3dfx claimed that they would get better yields out of the tried and true 0.25 micron process than they would by moving to a 0.22 or 0.18 micron process like their competitors. Thanks to the long delays in getting the VSA-100 products to market, this strategy has more or less backfired on 3dfx, leaving them with a slower, hotter, more expensive chip. To compound things, they're apparently not able to get enough chips out of their plant, TSMC in Taiwan, even though that's the same plant that NVIDIA uses.
The VSA-100 supports all T-Buffer effects, Full Screen Antialiasing, FXT1/DXTC texture compression and all of the other features 3dfx has been talking about for the past few months. For more information on those technologies read our in depth coverage of the T-Buffer here.
The VSA-100 supports anywhere from 4MB to 64MB of memory per chip, whose clock is synchronized with the core clock, just like the Voodoo3. The memory bus is 128-bits wide and will offer 2.7GB/s of memory bandwidth per chip. The excellent 350MHz RAMDAC of the Voodoo3 is carried over to the VSA-100, so 2D image quality is up there with the best.
From the above description, the VSA-100 doesn’t appear to be much more than a Voodoo3 with support for a few new visual features and 32-bit color rendering support, but the chip’s support for up to 32-way SLI scalability (hence the name Voodoo Scalable Architecture) is what truly defines it and sets it apart from the Voodoo3.