I've seen this before - some boards that do not support the 586 and a 4x multiplier... I have a FIC 486-VIP-IO2 - an OEM version that would not run with L2 cache enabled with a 586. Also, enabling 4x would result in the board forcing 3x and getting 100Mhz and no L2 cache. Setting 3x on the board worked fine. I did get the CPU to work correctly with a bios update.

Not all boards w/o official 586 support do this - some work fine and report a 133Mhz AMD DX4. Others hang, some run at 2x instead of 4x (2x is 4x for the 586), some like the FIC force 3x, others disable cache and so on.

See if you can find a 586 compatible bios update for your board.

meljor wrote:

Can i change it when the computer is running?

If you mean change jumpers while the computer is running, it will not work - the machine will hang. You might be able to change it in software if you're using a Cyrix 586 - but even so, the board will probably lock it at 3x and the machine might freeze. A BIOS update is your best bet.

Did you try switching from L1 WT to WB first thing after POST?

meljor: You are right in that running an Am5x86 at 150 MHz is pretty useless. While a 40 MHz FSB will normally run on the fastest of cache and memory timings (especially if you limit your cache size to 256 KB), 50 MHz FSB often requires the slowest of cache timings and 1 wait state for memory read.

Ok thanx guys. A bios update would indeed be the best bet but i don't know how to do that on a 486. My only experience is with flashable bios chips from pentium and up.

I just don't get it with these Amd 5x86 cpu's: they do not need anything from the bios as they are identical to the dx4's. The only difference is the 16kb cache and the 4x multi.

16kb works fine at the 3x multi so only the 4x gives problems. Why? Because the bios sees a 66mhz cpu (2x 33fsb setting is the same) with 16kb?

@feipoa: I know. My options now are 120mhz or 150mhz. 150mhz might be a tiny bit faster but it is pretty close because of the slow memory timings. 160mhz would be perfect.