2nd CPU Upgrade on Precision 670

Hey Guys,

I would like to add a second CPU in my Precision 670. Actually I have one CPU with this informations on my board:

informations on cpu-back:
2800DP/4M/800
SL8MA Costa Rica
L540A909-0134

informations on cpu-front:
2L5326677B
0137

Is it possible, simply to add a second CPU with exact the same informations (revision/model)!?

Also I bought a VRM (Voltage Regulator Module), a second fan and a passive cooler.

I tried already an upgrade with two 2800MP/2M/800 (SL8UB) CPUs, but it doesn't worked (only beeps after switching the machine on, fans run on maximum rotation).

I hope some of you could help me - it's not easy to find good informations for my CPU-upgrading problem - sites like processorfinder.intel.com couldn't help me out to find detailed informations which processor is working for me in a multiprocessor environment!

Greetings