Check this thread for lots of ideas:

How to slow down a windows 98 computer for slower games?

DosFreak's curated list of slow-down utilities may also be helpful:
List of Slowdown Utilities

amiga77 wrote on 2022-11-03, 16:50:

Hi, this is my first post :) […]
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Hi, this is my first post 😀

Can anyone help me, because I put the DOS system for old games on the PIII 750. It turned out that the parameters of the computer make the games run too fast. Can it be delayed somehow?

PIII 750 processor, P6VAP-A + motherboard, RAM memory, selectable from 16MB, 32MB, 128MB to 512MB 😀

Best regards and I wish you a peaceful day.

You can set CPU FSB to 66MHz in BIOS what will give you 7.5x66MHz = 495MHz. You can also disable L2 cache (small impact on performance) and L1 cache (big impact).
And because P6VAP-A+ has VIA chipset you can use CpuSpd - A Hardware Based CPU Speed Control Utility for DOS/Win9X Retro Gaming - its south bridge supports 16 throttle levels.

Thank you colleagues for the advice.

I decided to experiment with installing Windows 95 (osr 2.5) and my problems were partially solved as some fast-acting games in Windows 98 SE run normally without speeding up. Many games that didn't run under pure DOS or didn't run under Windows 98 SE on Windows 95 (osr 2.5) work. Thanks to everyone for the advice. Maybe someday they will come in handy.

Regards!