An excerpt from Hercules' TNT/2 Press Release lists this nifty overclocking feature:

Easy clock adjustment with Hercules HercuMeter™ Utility
Hercules' enhanced High-Performance/Wide-Bandwidth hardware design with about 3.0GB/second memory peak bandwidth takes full advantage of the RIVA TNT2's performance potential. An efficient active cooling device ensures board stability, even under adverse conditions. For further performance enhancement and flexibility, the Hercules HercuMeter utility allows users to fine-tune the Hercules Dynamite TNT/2's engine and memory clock for optimum performance. Maximum clock speed values vary with resolution, color depth and application.

Just in case this leaves you wondering, Derek Perez, Public Relations Manager at NVIDIA Corporation had this to say about 3dfx's comments:

"Clock for clock TNT2 is faster than VooDoo III. (One reason is that our fill rate is much higher due to our dual pixel pipeline) 3Dfx has no basis for their assertion that our part won't achieve high frequencies. They have no data on our process, design or yield. It is pure speculation."

And here is NVIDIA's position on TNT2 clocks from Dan Vivoli, Vice President of Product Marketing:

"The ultimate frequency achieved in end user systems depends on the chip cooling strategy, board design and the system environment that the board runs in. Each board vendor will make design and cooling decisions and environmental assumptions and spec the part according to these choices.

The RIVA TNT2 chips were designed to operate at extremely high frequencies. The Diamond V770 that you reviewed demonstrated that. With the right combination of advanced board design, intelligent cooling strategies and high quality manufacturing, I fully expect to see end users running TNT2 based cards at frequencies that meet or exceed the ones you saw in your testing."