Power edge 2950 - E1422 CPU Machine Chk - E171F PCI Fatal Error B1 D0 F0

It appears the CPU is bad either instead of the board or in addition to. A board fault may have damaged the CPU

1. Ensure it is not bad add-in hardware … remove any PCI/e devices in the system.

2. Ensure it is the slot and not the CPU … try each of the CPU's in the first slot (without populating the second slot) … if it won't boot with either CPU, then the motherboard needs to be replaced. CPU1 MUST be functional to use the board, there is no fixing it.

3. If the system boots but fails randomly with that error, then update the BIOS/ESM firmware.

Also make sure a proper layer of thermal paste was used when reinstalling the CPU

"E171F PCI Fatal Error B1 D0 F0"

That’s a PCIe error, nothing to do with the processor. Start troubleshooting by reseating all of your expansion cards.

Can be CPU, but I agree that it is more likely add-in hardware. On the 2950, it was very common BIOS issue where upgrading BIOS usually resolved it, but if you can't get the system to boot, that's not an option and would be something different.

When removing the cards, mind the RAID controller, which is not in a typical PCIe slot … it is located on TOP of the drive backplane, plugged into a PCIe slot on the sideplane.

You might also try simply clearing the NVRAM using the jumpers on the motherboard if all else fails.

I'd ask for a second replacement motherboard although we don't know which generation of 2950 it is, seen a few bad spares but they're cheap as so many made.

The 2950 is kinda archaic. There are dozens available on Ebay for under $100. If your customer insists on running old stuff, buy a couple and make one good one out of the parts.

Here is a bunch of five for around $150US.

https://www.ebay.com.au/itm/5x-Dell-PowerEdge-2950-2U-2x-Intel-Xeon-Quad-Core-CPU-Rack-Server/232746993283?hash=item3630cd4683%3Ag%3AfpEAAOSwImRYkV7i&_nkw=2950&_from=R40&rt=nc

Thanks for the help.
Took awhile to work this one out, with the customer stretching out the work.

Customer ended up replacing
CPU
RAM
System Board  (Gen III)
Hard drive that was currupting the array.

All adapters are replaced in the system.