Yes, I believe it is a Cyrix core, however it has the 8k cache (WB) according to CPU world so it should perform much the same as comparable intel or AMD chips. I'm not aware of any incompatibilities with the Cyrix 486, I thought those came later with the 6x86 but would be interested to hear more. I haven't used a Cyrix 486 CPU since they were new, I had a DX/2 80 myself and can't say I ever had an issue even being on a VLB motherboard with both I/O and VGA on that bus. Will be interesting to hear what others who have more recent experience have to say on the matter.
286 20MHz,1MB RAM,Trident 8900B 512K, Conner CFA-170A
386SX 33MHz,ULSI 387,4MB Ram,ALi M1217,OAK OTI077 1MB. Seagate ST1144A. Soundblaster 1350B.
Amstrad PC 9486i, DX/2 66(WB), 16 MB RAM, Cirrus SVGA, Win 95.
Cyrix MII 333, Rage Pro Turbo 8mb, SB16, WinME