For what purpose? You won't gain anything from it.

For my S3 Virge dx I use MCLK.exe and I have a Hercules that I can clock at 87 MHz and that provides a lot of speed gain. I am also looking for something like this for the NVIDIA RIVA 128 under MS DOS. Under Windows 98 with Powerstrip I achieve a 10 percent gain in both 2D and 3D. I would like to use the card under DOS 6.22, hence this question

There would be literally zero gains on that card, unless you heavily mismatch overall system power, like late Pentium 4 level.

For my S3 Virge dx I use MCLK.exe and I have a Hercules that I can clock at 87 MHz and that provides a lot of speed gain

S3 Virge DX were mediocre cards, which quite often were gimped by manufacturers on top of that.

It sounds unintuitive but you'll get a big speed gain by using a faster cpu like a pentium 2, because not all the 3d rendering was actually done on the graphics card. The graphics card needs to wait for some cpu operations for the rendering.

The problem is there's no DOS game with 3d acceleration for the Riva 128, while there are for the S3 Virge. Even if you overclocked the Riva 128 it wouldn't be used for 3d rendering, while the S3 is used in games that were made for it.

It is about Duke Nukem 3D in 800x 600 and Quake at higher resolutions and 2D acceleration in Windows 3.11.

egbertjan wrote on 2023-10-16, 15:02:

[...] Duke Nukem 3D [...] 800x600 [...] K6 3+ [...] enough CPU power available under MS-DOS 6.22

Uhm... that's far from being enough CPU power for Duke Nukem running at 800 x 600 (not to mention Quake).

egbertjan wrote on 2023-10-16, 15:02:

It is about Duke Nukem 3D in 800x 600 and Quake at higher resolutions and 2D acceleration in Windows 3.11.

There is no benefit when overclocking the card in games that uses software rendering. A faster CPU does improve the performance a lot in higher resolutions.

For VESA 640x400+ gaming in pure DOS, two things are important:
- Higher FSB speeds.
- Enable Write combining when the CPU supports it, after boot-up. (NVidia Windows drivers enable this too)

Benchmarks of the difference:
50 to 133MHz FSB on a BX Mainboard