Hello wxtwb,   I hope this helps.   With System board: Part# JC2W3 - ASSY,PWA,PLNR,SV,R820,NTPM,3   Compatible PEM: Part# 7TJ0F - ASSY,PWA,PEM,R820,NTPM  
Recently replaced the mobo in one of our PowerEdge R820 machines... I'm now getting "PEM cant not post: cpu in socket 4 did not come out of reset" Based off another post, I'm curious if the PEM we had previously is not compatible with the new mobo. NEW Motherboard DP/N: 0JC2W3 Old Expansion Riser Board DP/N: 08HJ4P If that is indeed the case, what P/N should I be looking for to add a riser to our R820? Thanks!
R820 PEM Compatability