Bought R710 with 1 x E5504 processor. Picked up a pair of L5639 which is the same processor family/socket. Replaced processors, put heat sinks back on but when I press power button server starts for 1 second and dies immediately. Tried with 1 processor - same story. Put back original E5504 - works fine. RAM is compatible. All seems fine.
What could be the problem?