Looks very like a Dell motherboard I've got. You want to look at the silkscreen between the cache and RAM slots for the 'C' jumper setting for the clock frequency. Then the silkscreen just to the right of the jumpers for the 'D' jumper settings for the CPU multiplier.

Max frequency on my board is 66MHz, with a x2.5 multiplier, for a maximum of 166MHz. There is a 'reserved' setting for the multiplier which might do x3 for 200MHz.

[currently your picture shows both 'C' and 'D' as 2-3 and 4-5, which is 60MHz x2]

Thank you. I've made progress. Changed the jumper D to 1-2 5-6 which gives me a 3x multiplier. so 180mhz. Not quite the 200mhz but close enough.

snufkin wrote on 2021-05-25, 19:05:

Looks very like a Dell motherboard I've got. You want to look at the silkscreen between the cache and RAM slots for the 'C' jumper setting for the clock frequency. Then the silkscreen just to the right of the jumpers for the 'D' jumper settings for the CPU multiplier.

Max frequency on my board is 66MHz, with a x2.5 multiplier, for a maximum of 166MHz. There is a 'reserved' setting for the multiplier which might do x3 for 200MHz.

[currently your picture shows both 'C' and 'D' as 2-3 and 4-5, which is 60MHz x2]

john81uk wrote on 2021-05-25, 19:23:

Thank you. I've made progress. Changed the jumper D to 1-2 5-6 which gives me a 3x multiplier. so 180mhz. Not quite the 200mhz but close enough.

If think if you set 'C' to 1-2 5-6 that should set the bus speed to 66MHz (that's the silkscreen between cache and RAM slots), so x3 that might get you 200MHz. If it boots.

One thing to bear in mind: that primitive linear VRM may not be able to supply the current required by the P200MMX. Maybe it's an idea to test first at 2.5x66MHz (166MHz) - the highest officially supported setting - and see how hot the heatsink gets. If you don't burn your hand or the CPU, then try 3x (RSVD). If that's OK, set it to 1.5x to try 233MHz (P55C remaps 1.5x to 3.5x)

Noted thank you. Seems ok at 180mhz so far but will street the CPU to see how it handles it.

dionb wrote on 2021-05-25, 20:53:

One thing to bear in mind: that primitive linear VRM may not be able to supply the current required by the P200MMX. Maybe it's an idea to test first at 2.5x66MHz (166MHz) - the highest officially supported setting - and see how hot the heatsink gets. If you don't burn your hand or the CPU, then try 3x (RSVD). If that's OK, set it to 1.5x to try 233MHz (P55C remaps 1.5x to 3.5x)

AN430TX used one linear regulator for 2.8V to support pentium MMX and take 3.3V from ATX PSU.

Cheers,