This is an So370 FC-PGA board, which electrically can support PPGA (Celeron Mendocino) and FC-PGA (P3 & Celeron Coppermine) CPUs. Without modification (of socket and very likely BIOS) it can't support FC-PGA2 Tualatin CPUs. Now, within the Coppermine family you have three potential limitations:
- max FSB supported by motherboard
- max current the VRMs can deliver
- max stepping the BIOS supports
Now, the P3-866EB was a 133MHz FSB CPU, so that's supported (no-brainer with Via ApolloPro133A chipset anyway), was released with the cB0 stepping, so you can be sure BIOS support that stepping. It draws 22.5W in that configuration. So you know that's good too.
The fastest mass-market Coppermine CPU is the P3-1000EB (P3-1100E runs on slower 100MHz FSB and does not perform better than 1000EB, and the P3-1133 was an abortive attempt to trump AMD that backfired when it turnet out not to be stable and had to be recalled). The only challenge is that the P3-1000EB FC-PGA was introduced with cC0 stepping (the only cB0 stepping P3-1000EB was Slot 1).
You can find the stepping of a CPU by searching cpu-world.com or intel.com on the S-Spec of the CPU (i.e. SL4C8).
Theoretically it's possible that this board has a BIOS that refuses to work with cC0 stepping CPUs, but I'd say that's highly unlikely. I'd expect that it says max 866MHz because that was the fastest CPU available at time of writing of documentation. There are several BIOS versions available for this board - can't find release notes, but I'd expect cC0 (and maybe cD0) stepping support would be in one of them: http://www.elhvb.com/supportbios.info/Archive … A133/index.html
As for the board and prices - all prices on eBay are stupidly inflated. This board ticks most of the boxes for a good late P3-system. It just lacks a fast chipset (ApolloPro133A is slow) and Tualatin support, but has ISA, two slots even, and is from a reputable - albeit now defunct - vendor. The ideal So370 system would have an i815EP (or perhaps SiS635T or ApolloPro266, er, or Serverworks IIIHE...) chipset and ISA. Unfortunately this combination ranks as unobtainium, you'll have to compromise somewhere, and no Tualatin support but real ISA slots is very acceptable for a DOS system. Tbh, you won't benefit from the CPU upgrade at all for DOS, but for Win98 (SE I hope) games it will make a noticeable difference. Another motherboard probably won't, I'd keep this unless you hit very specific issues.