Hmm...

The Voodoo3 can run as 2x AGP, if I'm not mistaken.

There won't be any real advantage though, since no 3dfx Card ever supported AGP Texturing (which would be the only thing to really benefit from 2x or 4x).

So there's nothing to be concerned about, Textures are commonly loaded only once at startup onto the Card, and normally remain there in most cases

One of my Voodoo4's (a Powercolor Model w/ TV out) is claimed to be 4x AGP onto the Package and in the Manual, but I could never really confirm that.
That would be the only 4x AGP 3dfx Card I would know of, all others (V3, V5) are max. 2x AGP as far as I know...

Modern Drivers allow you to select 1x or 2x AGP in the Advanced Property sheet; otherwise setting it to 2x in the Bios should make it work as well...
(But as said, no real advantage, even in Benchmarks)

On a sidenote, I would also recommend not to take everything for real that SiSoft Sandra reports...
It's a fairly useful program, but has some shortcomings (= isn't always really accurate)

Greetings
FalconFly