Using TNT2 Video Cards With 133 FSB

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Intel recently started making some of their Pentium III 450 MHz processors from P3-550 and even P3-600 parts. It seems that they just set the internal multiplier to 4.5, but use the same silicon and cache memory, either Toshiba-300 (3.3ns) or NEC-A36 (3.6ns). Just a rumor, yet it sounds reasonable. Indeed, why should one use more expensive ram with a real 450 part, for which
4ns is more than enough?

Anyway, those “remarked” P3-450s are now available in many places. They are OEM parts with the following S-code on the top edge of the plastic back: SL35D. And they often cost even less than retail boxed P3-450 (coded SL37C). Be sure to check the cache chips though, not every SL35D has those fast ones.

Well, this all would be just great if the multiplier was not locked. But since it is 4.5, the only way to get that magic 600 MHz is to use 133 MHz FSB. Ok, and why not? This is why. Intel 820 and 840 chipsets are still somewhat away from the mainstream consumer. And VIA Apollo Pro 133 doesn’t perform well enough. So, most of us stick with the good old BX chipset that doesn’t have 1/2 FSB to AGP divider.

There are only 1/1 and 2/3, which gives minimum 88 MHz AGP at 133 MHz FSB. The problem here is that almost none of TNT2 AGP cards can stand that much. At least this is the first and most probable conclusion one would come to. Is there any way around? Actually yes, and there is more than one.

METHOD I: Just don’t use that damn AGP, use PCI instead. Most modern BX mainboards provide 1/4 PCI divider at 133 FSB, which makes perfect 33 MHz of PCI clock. The best choice of a PCI card is obvious, Voodoo3 2000 PCI. Just be sure that the card has Hyndai TC-7 memory, and 175 or even 183 MHz is almost a sure bet.

This way works 100%, but it would require one to sell or put away that TNT2 and start all over with a Voodoo and with no 32bit color, and no 32 Mb RAM, and so on.

Ok, but what if I want to stick with my new and expensive TNT2 Ultra card? Is there any hope for me? Yes. But again, there is not just one way for that either.

METHOD II: Set AGP aperture to 4 MB in your mainboard BIOS Setup. This effectively disables any AGP texturing. Actually, even if some application really needs and can use AGP textures, 4 Mb is not enough for that.

METHOD III: Keep the AGP aperture to the standard value of 64 Mb or whatever you usually choose. But disable AGP Side-banding. This can be done either by re-programming the video card bios as for Asus v3800 TNT2 cards, or simply via the drivers as for Creative TNT2 Blaster cards (just mark “Disable AGP” option there). More details and technical explanations about AGP Side-banding can be found HERE.

Both Methods II and III seem to work OK. The results are different though. Below are some 3D Mark 99 MAX results, all taken at the default benchmark settings (800×600, 16b color, 16b Z-buffer) and using the same system:

Asus P3B-F, SL35D P3-450 with NEC-A36 cache, 128 Mb SEC -GH RAM, Asus v3800 Ultra with core/memory clocked at 166/210 Mhz. The results:

(P3 450 at 630 MHz, Asus v3800U, AGP aperture 64 Mb, Sideband OFF) – 6,219

(P3 450 at 600 MHz, Asus v3800U, AGP aperture 64 Mb, sideband OFF) – 5,979

(P3 450 at 630 MHz, Asus v3800U, AGP aperture 4 Mb, Sideband ON) – 5,941

In addition, the same system with a PCI Voodoo card:

(P3 450 at 630 MHz, Voodoo3 2000 PCI at 175 MHz) – 5,536 3DMarks

The conclusion is obvious: Use Method III – keep AGP but disable side-banding. And enjoy your new cheap P3-600, your good old BX mobo and last but not least your beloved TNT2 card.

– Eric


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