It has been 2 years since we noticed it after checking some invoices (for other things), we have had 2 Server 2008 R2 RDP servers playing up on & off for years. It may be related but maybe not.
We have 2x HP BL460c's in our chassis and the supplier mucked it up and put in CPU #2 as a lower spec'd CPU (see url: http://ark.intel.com/compare/33080,33079
- both CPU's are listed)
Would the fact that 1 CPU does not have Idle States, Speed Step & Demand Based Switching whereas the other does? From memory the Speed Step options are set in the BIOS also..
We also have another server - a BL480c with an E5430 & E5410 but it runs fine - Bar showing that they are listed at 2.66GHz but are stuck running at 2.33GHz.