Well he sold as for parts so he probably didn't care about protecting it all too much. I'd look for any small scratches on the PCB or if there's any missing surface mount components. Worth a shot before you stick 'er in the oven.

Edit: I re-read your post. I'd definitely make use of that microscope to see if there's any damage to surface mount components. Sometimes they can look okay to the naked eye but up close they maybe damaged or have bad solder joints.

Here are a few pics of the CPU I took in the morning.
Seems like one corner might be a little chipped. Oh well. Or is this something "normal"?
When I have a few moments of time I'll have a look under the microscope

That's a flip-chip design IIRC, such a tiny piece missing on what is the back of the substrate shouldn't really kill the CPU. Clean the gold pads with IPA, make sure you have good contact in the slot.

I've cleaned the contacts with IPA and also using a DEOXIT-pen.
I did manage to get it to show some post codes (can't recall what) but haven't been able to reproduce it.

oh2ftu wrote on 2024-05-28, 13:52:

I did manage to get it to show some post codes (can't recall what) but haven't been able to reproduce it.

On this mobo or known good one? Because it could be a slot issue, these are not very robust - I have heard stories about bad slots. Usually issues developed by twisting the CPU too much, sometimes in transport, because of the side supports missing (or broken), or not doing their job (some Slot1 CPU packages require special "caps" on the corners to sit tight, these caps are the first thing to go missing when the CPU is removed and resold).