It depends on what kind of cards you have on the AT bus. In most cases, I would strongly advise against clocking the AT bus over default 8MHz. Soundcards and SCSI cards in particular are pretty picky.

Yep. Seems the performance gain is negligible with a VLB/PCI system anyway.... In my case, speeding up the VLB bus should do more effect. But I prefer stability/compatibilty. I guess I could throw a DX4/100 in there instead...

I've usually found that about 10 MHz is okay. I used to run my 486 with the FSB at 40 and ISA at FSB/10. Speed boost? I doubt it. I've read that it can be useful for ISA NICs, but if you need NIC speed you need a new bus and need to get rid of that ancient NIC! 😀