[Scutter]

I found this document that has a brief mention of adding a second processor. This is what it says:

How do I add the second processor to the HP xw6400 and xw8400 Workstations? Is a system board swap required?

CPU upgrades are field and customer installable without system board swaps using the HP xw6400 or HP xw8400 Workstation CPU upgrade kits. The second processor must be the same speed and stepping as the first.

[MeganC]

The CPU’s are identical. I checked that first before I installed the 2nd one. Also put on new thermal paste.