Thanks Nige, yes, it looks like we agree where the 25MHz clock is but now I've changed my mind ;-) If I use this board then have the potential to blow it up and as it's my active system that's too much of a risk. So, I'm changing which board is being prep'd for surgery to an INTEL S1200KP - as it's currently spare.
Any kindly moderators that are reading this would they mind changing the thread title to: "INTEL S1200PK motherboard clock identification"...many thansks ;-)
The 1200 board will boot direct from linear but it needs a -12v supply in order to do this. A pain but there we go. Luckily I've got a linear psu in the bits box so I'm good to go. I'll prolly use a pico for testing anyway as there are too many things to go wrong otherwise.
So, now the hunt is on to find the clocks on this new board. Please see this pic and see if you concur with my thoughts:
Three 25MHz clocks. Each with "H253C" on the casing.
Some close up shots (these are of my actual board, the above is stock, hence the silver clocks above and the black ones below). You can also see that the PCB markings show 25MHz very close to some of the clocks:
One final one without the southbridge heatsink (along with fully-naked thumb!!!)
I've been trying to find out what the component is so that I can work out the pinout. Any ideas? Or is it possible to tell which pin is which from the circuit? Each of them have 4 pins and have H253C on the casing. Beyond that not much progress.
If I can work out which pin is which then my initial plan is to remove one clock, mount it on a separate PCB and feed the same clock lifepo4 power. If I can't workout the pinout then I'll need to remove the clock, power the board and then check for ground and voltages. Then try to decide which of the remaining two is the clock output (gulp).
Cheers for any help,
Crom