While browsing the internet looking for information on virtual machine sizing, I came across the following comment: "AN Intel XEON Dual Core CPU has e.g 2 x 3000 MHZ. The Second Core is only 50-75 percent equal to the first core."
I can understand that there could be a bit of overhead between cores, but this sounds rather extreme, so I was wondering if there was any truth in this statement.
Please note I'm not talking about mobile phone CPUs where this is actually intended behaviour (performance versus power usage), I'm talking about desktop/server CPUs where each core has the same speed.
So in for instance a quad-core CPU running on 3Ghz, is there a big difference in clock speed between the cores or not? And if so, why is there a difference and why is it that big?