Ran into another quirk with my KT7A-RAID.
Under DOS 6.22, I was getting quite noticeable and distracting crackling noises from the MK1869 XTREME (ESS ES1869 and Gravis UltraSound PnP) sound card I am using. It was especially noticeable when playing Duke3D.
The FAQ website by Paul that I linked last page was quite useful for resolving this issue.
It suggested disabling Delay Transaction and PCI master Read Caching in the BIOS. This is done by default with newer BIOS revisions. This reduced the crackling by a little but it didn't fix the issue.
The site also suggested reducing the I/O voltage or overclocking the FSB slightly. In my case, reducing the I/O voltage made it much worse but increasing the I/O voltage by one tick (0.10v) pretty much fixed it. It is night and day compared to before. I MAY hear a random crackle sometimes (I'm not sure if I'm imagining it) but that's very rare, whereas before it was crackling multiple times every few seconds.
I also tried increasing the FSB but that seemed to bring back the crackling even with the above fix. So you may need to adjust both the FSB and I/O voltage to sort it out.
So to summarize, with my Barton-M 2500+, I am using 9x multiplier (With the 5-4 PIN mod, so it's actually set to 17x multiplier), 133 FSB, CPU voltage set to 1.65v (May be able to lower it to somewhere between 1.6v-1.65v, but 1.65v is 100% stable so haven't bothered yet), 3.50v I/O voltage and the rest of the BIOS settings are set to what is recommended on Paul's website.