Question Back case fan running fast after replacing Intel Xeon W3520 with Intel Xeon 3670

Reviting

Honorable
Dec 18, 2014
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Hi, all

So here's the backstory - I've had a HP Z400 Workstation for some years now, running on Intel Xeon 3670 CPU (in US). I recently moved to EU and bought the same HP Z400 workstation with an existing Intel Xeon 3520 CPU.
Before moving, i gutted my old Z400 - taking with me the ATI graphics, CPU fan, the CPU (Inte; Xeon 3670) and the WiFi antenna. Had no trouble replacing the graphics and the WiFi. I waited few weeks before replacing the CPU cuz i wanted to get thermal paste first.

So after replacing it (the CPU), the fan at the back of the case started running normal (after pressing the power button). Within half a minute or so, the fan's RMPs jump real high and stays at that level. The screen doesn't receive any signal at all. Keep in mind i did put thermal paste.
I shut the PC off again, put back the old CPU (Intel Xeon 3520), put the thermal paste again (after wiping things out), while keeping the CPU fan that came with (Intel Xeon 3670 - the one i brought from the states) on. Turned the PC back on and it booted just fine.

The motherboard of the HP Z400 (that I got in the EU) is HP 0B4Ch, Chipset - X58, I don't have the motherboard's info I had in US. Based on that sheet ( that i found here), both CPU's are compatible.


Any suggestions why the back-case fan jumps RPMs after putting the Intel 3670 CPU in place? Do different power supplies (US and EU) have anything to do with it?

Thanks,