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Scott Sellers on the VSA-100

Scott Sellers is the man that put the first "S" in SST, the internal product designation for all 3dfx chipsets. From his beginning as one of the original three founders of the company, Scott has since become chief technical officer, overseeing the diverse elements of engineering, designing, research and development that go into the creation of each and every piece of silicon that has the 3dfx logo stamped on it. While Scott has just successfully overseen the delivery of one baby - daughter Kristin Cole Sellers, born November 1, 1999 - he’s impatiently awaiting the arrival of his next, the VSA-100 Engine that is the core of the Voodoo4 and Voodoo5 products. We managed to pull Scott off the phone and away from his e-mail for a sixty-minute conversation about 3dfx’s next progeny.

: So, you’re a daddy now.

: Yep, sleep deprived and weary. It’s very hard to have a silicon baby in the works at the same time. Fortunately, my wife’s mother will be in town during Comdex next week to help out, but I’m going to try to get out of there (Las Vegas) as soon as possible.

: What kind of frame rates can we expect from this soon-to-arrive silicon baby?

: It really depends on the type of game you’re playing. For the Voodoo5 5000, we’re targeting 60 frames per second at 1024X768 with an 85Hz refresh rate and 32-bit color turned on. And for some games we can also hit this performance at 1024x768 with 32-bit color and full-scene anti-aliasing enabled. This is very application dependent, of course, so you might see some games running at that speed at 1280X1024, but that would be with the more simple games.

: Is the VSA-100 Engine, the chip that powers the Voodoo4 and Voodoo5, still based on the original Voodoo Graphics core, or is it an all new design?

: It’s somewhere in between. The VSA-100 is still based on the Voodoo Graphics core, for compatibility reasons, but we’ve made significant changes to the overall design. We had to build in support for 32-bit color, 2 pixels per clock rendering, new texture modes, new combine modes, tremendous scalability improvements, support for texture compression, larger texture sizes and a number of other new features. At heart, it’s the Voodoo core, with lots of substantial changes. As a result, we consider it to be really close to a new architecture.

: While I think that most of the computer gaming world understands the concept of SLI with two cards, the Voodoo5 family is producing the same effect on a single card. How does SLI work on a single board?

: We no longer have the ability to plug two boards together as we did in the past, because the VSA-100 has been optimized for AGP. We don’t have the upgrade capabilities that we did with the PCI Voodoo2 boards, but this is also a good thing, since you’re not burdening your system with two slots.

SLI technology is done a little differently now. With the Voodoo2, each chip was rendered every other scan line and then the two images were combined. With the VSA-100, each chip will render a programmable number of scan lines, up to 128, and we can dynamically change the band height to maximize performance. So in a four-chip solution, like the Voodoo5 6000, each VSA-100 will render something like 32 lines. The first chip will render lines 1 to 32, the second chip will render 33-65, the third will do 66-98 and the fourth will do 99-128. This is a much more powerful solution than Voodoo2 because it gives us the ability to use more than two raster engines -- that’s how we end up with products like the quad-chip Voodoo5 6000 and Quantum3D’s 32 chip AAlchemy system.

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