Some boards will work that way, some don't.

Oh, I see.. Well, I'm asking because I have two boards I am considering using for a Cx5x86 build..

One is a Biostar MB-8433UUD-A which currently has no cache (no big problem, I can transplant that from a VLB board that I've had issues with - specifically not being able to load anything into UMB for some weird reason) and a dead Dallas RTC soldered on (desoldering which, I am really not looking forward to..).

The other is a PCPartner 486VC which seems to be an all around decent motherboard but does not seem to have any explicit compatibility with Cx5x86 CPUs..

It's not always a hard requirement, but the Cx5x86 is definitely the most advanced So3 CPU with a lot of settings that can be incorrect. My experience is that Cx5x86 will generally only work on board that explicitly support it, whereas Am5x86 (a much simpler 486 design clocked very high) basically runs on anything that can give it correct voltage, or with an interposer on pretty much any 486 board at all. You may miss things like WB-cache support on really old boards, but it will run.

So I'd give you more chance on the Biostar. However in this case the boards are virtually identical with a chipset that shouldn't have any problems with Cx5x86. It's worth a try at least.

appiah4 wrote on 2020-01-29, 07:49:

Would a motherboard necessarily require to explicitly state compatibility and jumper settings for Cx5x86 processors or would being compatible with Cx DX processors and having the required voltage settings be enough for it to work with the CPU?

Cyrix Cx586 CPU uses the Intel DX4 pinout which is a different thing than Cyrix DX or M7 pinout. So if there is no explicit Cx 5x86 setting the Intel DX4 is the one to go.

Sadly Cx586 is quite a complex chip and there is no guarantee it'll work on a particular motherboard until it actually works.