No. Multi is fixed at 2X.

If you get an old MICRONICs 486 ISA motherboard the clock speed is set by a socketed oscillator, I stole some random oscillators off failed video cards and had fun overclocking and underclocking the system

Also the ISA divider was fully adjustable from 1x (bus) to ????

In theory boards of that type could run your processor at any speed, even a couple MHz

Run the bus at 12.5MHz and you get 25MHz CPU clock, though performance is gonna be worse than 25MHz CPU and 25MHz bus. At least you can use your slowest memories 😜

There are motherboards that can set interesting bus speeds even without a socketed crystal. For example my FIC 486-GIO-VT can go as low as 8MHz. Or even lower but I could never boot the 2 and 4MHz settings... Even 8MHz was no good as it forgot how to write my HDD at that speed... 16MHz, on the other hand, worked perfectly both with ISA and VLB cards. 2x16MHz should give you 32. Not exactly 25 but not bad.

It's probably more convenient to just buy a real DX-25.

Just get a DX-50, then you're covered for all bus speeds.

Anonymous Coward wrote:

Just get a DX-50, then you're covered for all bus speeds.

And you are in for a lifetime of pain trying to get your hardware running on a 50MHz VLB 🤣

appiah4 wrote:

Anonymous Coward wrote:

Just get a DX-50, then you're covered for all bus speeds.

And you are in for a lifetime of pain trying to get your hardware running on a 50MHz VLB 🤣

Yes, For a VLB motherboard what is the best CPU to use in order to run slowest ?

486sx25 ?
486dx33 ?
486dx-50 ?
486dx-66 ?
486dx2-50 ?
486dx2-66 ?
AMD 486dx40 ?

I want to be able to play old DOS games that require a slow CPU. Like “wIng commander”.
I can use the turbo button feature and disable L1 Cache with “Setmul” utility to slow down the CPU even further.

Any of the DX/SX chips without internal multipliers will run at margin of error differences at 20MHz FSB if your board's clock generator can do 20MHz. Then you can disable onboard cache and that should bring it down to 386DX levels. If you also disable the internal cache (setmul should be able to do that I would think) you'll probably end up at AT speeds? If you have a functional Turbo header on the board using that could bring you down to XT speeds or so? Test and see 🤣