I had one of those that came with a Cybermax system that was given to me by a friend, and it was initially equipped with a Cyrix CPU. Knowing very little about computers at the time, I bought a200 MHz Evergreen upgrade CPU (actually a WinChip) from Ebay, and the board wouldn't POST. I emailed Evergreen, and they suggested I update the BIOS to the latest one. Having never done this before, I may or may not have upgraded to the latest from Biostar for the board - either way, it still didn't POST with the Evergreen CPU. So they emailed me a BIOS (I was having to swap back in the Cyrix CPU to use my computer) and that time I know I did successfully do the update. And after that, it POSTed with the WinChip CPU! Later on I put a 450 MHz K6-2 in it and ran it at 400 (6x66) and it worked until the CPU voltage regulator overheated and blew.

So if you can find a newer BIOS than what you have, try that first. I hope that works for you because I doubt there's any way to get the BIOS that Evergreen sent me back in 2001.

The interposer should allow you to run lower core voltage to the CPU, but I don't know that you'll need to (IIRC the board goes down to 2.6); it won't change the speed, other than possibly allowing you to run a faster CPU without overvolting it.

Also, it was very cool of Evergreen to be so helpful - I bought this CPU used, so that was very impressive.

This may be the issue: what revision is your board? I have no idea what version mine was.

"Revisions older than 2.3 can only run Pentium MMX or Cyrix MII up to 166 MHz (classic Pentium 200 is fine). Revisions from 2.3 and higher support the MMX and MII CPUs up to their maximum 200 or 233 MHz (3.0x or 3.5x multiplier)."
http://www.dosdays.co.uk/topics/Manufacturers/biostar.php

It's a rev 1.1, so looks like i can't go above 166. Would that still be the case with the interposer?

UPDATE: So i got it to boot with the K6 233 cpu by setting the bus speed to 60mhz. It shows it as running at 210mhz, but i'm not sure that's right since changing the multiplier jumpers doesn't change that number. It hangs on the next screen and won't get to the next part where it boots from either a floppy or disk. Disabled both internal cache and external does let it boot to dos, but it's dog slow. Any ideas how i can make it work? Otherwise i'll just put my mmx200 back in.

f34rthereaper wrote on 2021-12-02, 18:27:

It's a rev 1.1, so looks like i can't go above 166. Would that still be the case with the interposer?

UPDATE: So i got it to boot with the K6 233 cpu by setting the bus speed to 60mhz. It shows it as running at 210mhz, but i'm not sure that's right since changing the multiplier jumpers doesn't change that number. It hangs on the next screen and won't get to the next part where it boots from either a floppy or disk. Disabled both internal cache and external does let it boot to dos, but it's dog slow. Any ideas how i can make it work? Otherwise i'll just put my mmx200 back in.

If you have the newest BIOS for the board, then I don't think there's anything else you can do since it sounds to me as though it's a BIOS recognition issue.

Your boards power regulators may be too wimpy for faster chips.
If you have a linear I bet it’s getting toasty enough to fry an egg.

An interposer for a k6-2 upgrade with its own power connector should solve any voltage/ power regulation issues and also let’s you set voltage / multipliers however you want

Sorry for resurrecting such an old thread, but I think I can add some interesting info here.

The limit on the older revisions of the board are based on the fact that Biostar did not anticipate that Intel would change the BF0 / BF1 settings and that there would arise a need at some point to actually pull those lines high.
But this is needed to use certain higher clocked Pentium MMX cpus.

I found a link where some guy explained this in more detail and also shows a small (yet reversible) modification with basically two jumper, two wires and one resistor to make those MMX cpus work.

https://www.vobarian.com/8500tvx.html

Whether the voltage regulators can actually supply enough power to safely run these buddies I don't know.