second CPU reduce single-core performance?

[Filin]

When I delided a pair of my X5680s, first I ran the system with a single installed CPU, did some tests and after that installed the second CPU and again did the tests.

With one X5680 installed Geekbench single-core was around 3,100. When second X5680 was installed single-core reduced to 2,800.

Does anyone know the reason for this strange fact?

 

[ActionableMango]

When I delided a pair of my X5680s, first I ran the system with a single installed CPU, did some tests and after that installed the second CPU and again did the tests.

With one X5680 installed Geekbench single-core was around 3,100. When second X5680 was installed single-core reduced to 2,800.

Does anyone know the reason for this strange fact?

It is normal for Geekbench and certain other applications too. Additional cores in a single CPU doesn't seem to hurt (i.e. moving from 4 to 6 cores for example), but going from a single CPU to a dual CPU can lower single threaded performance a little bit in certain cases.

I have no idea why this happens, but I can at least assure you that it is expected.

 

[ActionableMango]

Actually here is a post from just this morning that shows the same thing. Geekbench roughly 3100 with one x5690 processor and roughly 2900 with two processors:

https://forums.macrumors.com/threads/12-core-2-66-to-3-46-upgrade-worht.2042644/#post-24551605