The CPU is actually running at the specified CPU speed (except perhaps when selecting the 3.5x multiplier), it is just that during POST it doesn't display the correct frequency which means that the motherboard may don't actually have the latest BIOS. This can be somewhat checked by looking the date at the bottom of the POST screen.

During post at the top for the year under the bios version v4.51PG is 1984-96 and at the bottom of the screen is:

09/23/96-i430VX-W877-2A59GD4FC-00

I have tried a known good Pentium 200mhz mmx from another board and its the same, speedsys and other programs say its only running at 166mhz but at least speedsys reports it as a P554c

Could there be a different jumper setting than the manual for the multiplier? I'm still holding back on that though ide like to know about the bios first

You can try 66MHz*1.5 and see what happens。

There is a difference between P54C (non MMX) and P55C (MMX) in interpreting multiplier.
Please watch this great explanation from Scorp: https://youtu.be/J0NLGfocviU?t=282
But this can be remedied by soldering a resistor - details also in this video 😀

Jumpers are directly connected to the CPU's BFx pins - it shouldn't be BIOS dependant, only if the correct speed is shown at POST or not. But if softwares show that it runs at 166, that's probably the case. I would probably try some other multiplier settings to see if they'd work. Until you wrote that you tried a known good 200 with same result, I was considering, that you might have a counterfeit 166 with locked multiplier, but that doesn't seem to be the case ...

Thanks for the video zyga64 I'll look into adding a resistor on the BF0 to see if it helps but I might need some help with which of the jumper legs to use on this motherboard I can find the BF0 pin on the underside of the CPU socket though, zwrr the setting for 1.5x uses the same jumper setting for 3.5x JP8 1-2 off, 3-4 off, it runs at 133MHz for both settings its a bit strange that there is one settings for two multipliers

GabrielKnight123 wrote on 2023-11-21, 11:45:

Thanks for the video zyga64 I'll look into adding a resistor on the BF0 to see if it helps but I might need some help with which of the jumper legs to use on this motherboard I can find the BF0 pin on the underside of the CPU socket though, zwrr the setting for 1.5x uses the same jumper setting for 3.5x JP8 1-2 off, 3-4 off, it runs at 133MHz for both settings its a bit strange that there is one settings for two multipliers

It's by design. Because processors which supports x1.5 doesn't support x3.5, and vice-versa.
Take a look here: https://www.pchardwarelinks.com/cpuspeed.htm

GabrielKnight123 wrote on 2023-11-21, 08:00:

09/23/96-i430VX-W877-2A59GD4FC-00

Definitely not the latest BIOS for that motherboard.

There are later ones which can be found here, yours has the COAST module so pick the one mentioning 07/31/98-i430VX-W877-2A59GD4FC-00.

I have noticed that sometimes the multiplier settings are sometimes scrambled on locked p1 mmx cpus

There are two registers you must fiddle with

Bf0, and bf1

You should also make sure these pins are pulled high when pull low (jumper) is removed

You can remove cpu and measure these pins for 3.3v with mobo turned on and bf0,1 jumpers removed.

You can check them again with mobo off and jumpers installed for continuity to ground (black, negative)

Past that, if that checks good just fiddle with those settings until you get 200mhz as I said some of rhe locked cpus had their multis scrambled.

I have some same S-spec cpus that between three different specimens will give three different multipliers without changing the mobo 🤣