Overclocking the TNT

by Anand Lal Shimpi on September 13, 1998 8:53 PM EST
On the phone with a good friend of mine, Manveer Wasson, joking around about the usual an idea hit us both that would prove to be a challenging yet extremely beneficial experiment. 

AnandTech Exclusive

At the time of testing the Canopus Spectra 2500 I found myself admiring the excellent design of the heatsink/fan combo Canopus outfitted their first Riva TNT based card with, Manveer poked a little fun at my extreme admiration of the fan by telling me to develop my own cooling solution.

This is when the idea hit us, nVidia developed the Riva TNT with the intention of running the chip at a 125MHz clock speed, so why not give it a try at that clock speed? Due to the price of 0.25 micron silicon real-estate, and the increasing pressure to release a competitor to 3Dfx's Voodoo2, nVidia was forced to ship the TNT manufactured on 0.35 micron silicon wafers.  The greater the thickness of the silicon manufacturing process, the more heat the processor will generate, and therefore nVidia managed to eliminate the possibility of running their highly anticipated TNT chip at the 125MHz they originally proposed.  Here's where the problems begin.

Proposing an Acceptable Alternative

You must keep in mind that nVidia built the TNT to run at 125MHz, unlike the Voodoo2 which was designed to run in the 90 - 95MHz range and unlike most system microprocessors which are designed to run at their official clock speed alone, the TNT was manufactured with the intention of being run at 125MHz.   Once the first revisions of the literally flaming 0.35 micron silicon hit the hands of the engineers it was obvious that a change in the recommended clock speed had to be made.  Initially the change was supposed to be from 125MHz down to 100MHz, however instability at 100MHz required that the drop from 125MHz down to double digits be made in order to ship a reliable product.  Just about a week before releasing the TNT chipset to the public, nVidia changed their recommended clock setting once again, this time to 90MHz to increase stability.

A Lower Clock Speed Means Lower Performance

As you might be able to guess, this drop in clock speed also resulted in a drop in performance.  The original specifications for the Riva TNT chip indicated a 250 million pixels per second fill rate which would put it over the top of the Dual Voodoo2 SLI setup that had reigned for the past few months.   However that 250MP/s fill rate was calculated using a TNT clocked at 125MHz, not at 90MHz.  At 90MHz, the fill rate drops to 190MP/s, conceptually still much higher than a Voodoo2 but in reality not all that much better.  In an attempt to explain the lack of the TNT being the proposed Voodoo2 SLI killer it was initially dubbed, nVidia reassured the public that early in 1999 they would make the move to a 0.25 micron manufacturing process for the TNT and release a revision of the chip designed to run at full speed, being 125MHz.  In theory, once nVidia makes that jump, we should have a definite Dual Voodoo2 SLI killer on our hands...right?  Well, what nVidia wasn't counting on was an actual test to prove this theory, hang on to your seats, as AnandTech managed to develop a custom made cooling system made specifically for the Riva TNT chipset which allowed it to be clocked at 125MHz and beyond!  How were the results?  Is the next revision of the TNT worth waiting for?  Did nVidia "bend the truth" with the possible performance of their TNT chip?  Let's find out as we push the limits of nVidia's 2D/3D wonder in an AnandTech exclusive, Overclocking the Riva TNT - Current & Future Expectations.

The nVidia Riva TNT - Current Expectations

It is obvious a great portion, this editor included, of the PC enthusiast population became preoccupied with the search for the elusive Voodoo2-killer.  This whale hunt ended in much disappointment, but fortunately, it managed to provide for a wonderful combatant against the hype that many manufacturers had to generate to promote their products over 3Dfx's reigning king, the Voodoo2. 

A Direct3D masterpiece, the Riva TNT chipset already provides performance greater than that of a single Voodoo2 and comparable to a Dual Voodoo2 setup under Direct3D situations on virtually all processor platforms, Super7 excluded.  The TNT's OpenGL performance will be improved in the near future with better drivers and a more thoroughly optimized ICD, however currently, the TNT already provides with performance that is around the mark of a single Voodoo2 while offering clearly superior image quality.  All of this can be achieved for a price tag falling in the $169 - $199 range.  The extremely competitive 2D performance of the TNT rounds off the extremely positive outlook the TNT will give even the most pessimistic user.   You want to keep in mind that the Riva TNT is still the best option for a well rounded 2D/3D accelerator, and definitely gives 3Dfx a run for their money, but is it a sin to want the performance nVidia originally assured we would be getting?  Not at all in the mind of this overclocker...

The Solution & The Test
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