The clock is not likely software configurable, and even if it were, I believe the 2D engine core clock runs synchronous with the VRAM. I'm not sure an OC from 60 to 83 Mhz would be healthy. Last, I doubt you'd see a major improvement in real performance. 2D pixel pushing was much less of a performance barrier by this time (unless the graphics card was truly terrible).

AFAIK there are no utilities for DOS that can handle a lot of video chips.
That said, there are specific solutions for a lot of chips.
For Voodoo cards you would just set the relevant environment variables.
For S3 chips (and some other) MCLK is the weapon of choice. Read the documentation, lots of interesting information I don't want to repeat everything here. @gdjacobs: AFAIK S3 chips use different clocks for core and RAM. Voodoo chips use a synchronous clock.
I don't know if the memory clock is really a restriction. It is possible that you only gain performance in accelerated GUI operation (ie. Windows) and DOS games won't run faster.
One relevant not from the MCLK docs: "Some video BIOSs reset the DRAM-freq registers". I noticed that with my STB Nitro 3D (Virge/DX). I might one day try to mod its BIOS, probably only in the shadow RAM.

idspispopd wrote:

For S3 chips (and some other) MCLK is the weapon of choice.

Indeed! I tried it in my Eagles Trio64V2/DX w/ 2MB 35ns EDO memory and it can easily beat 71 MHz with cpu-2 mem-3 timings at 1-cycle EDO! (a bit unclear explanation, but who cares? 😀) It gives me a nice boost in VESA modes (for banked one from 22 MB/s to 31.4!) and 1 additional fps in Quake 😀

You can also try S3 SpeedUp for speeding up banked (not linear!) VESA modes (it can also boost VGA 13h mode but I can't recommend it because it does not work properly with Doom and other Mode-X games).

idspispopd wrote:

AFAIK S3 chips use different clocks for core and RAM.

Not sure, but I think that S3 chipsets (prior Savage3D I guess) use same clock for memory and core.

@idspispopd

Can't find any mention of the Trio asics or any of the utilities having or being able to access a second clockgen for VRAM. Doesn't really make sense in this use case. I would be quite happy to be wrong, though. I'm here to learn!

@wbc: You didn't mention if you already use s3vbe20, but since you know about s3spdup I suppose you also know the first one.
@gdjacobs: Well, mclk documentation only talks about memory clock. Of course it's possible that the whole chip will be clocked faster. I didn't find anything conclusive on vintage3d.org, although the database table lists different clocks for Virge/GX. Perhaps PowerStrip would tell more? Since the core doesn't seem to limit the overclock much I probably wouldn't worry, but if in doubt you could slap a heatsink on the chip.

idspispopd wrote:

You didn't mention if you already use s3vbe20, but since you know about s3spdup I suppose you also know the first one.

Yes, I used it, although I suppose that it can work without it by fact (according by this doc)