"2006 Xserve Dual x5365 Xeon Upgrade
I just wanted to let you know that I have an 2006 Xserve with 32GB of ram running OS X Lion that I dropped a pair of 3GHz quad-core X5365s into. (Ref: Intel X5365 info.) There was no need for a firmware update like on the Mac Pros (*see note below) and it screams now. What used to get the CPU percentages up now barely registers in the system monitor.
   This system (originally) had a pair of 5160 dual-core 3GHz CPUs in it. I got the X5365's off eBay for about $150. This is a quick and easy upgrade that brings new life into the server. The fact that it has G0 stepping also means that it uses little to no extra power and the temps stay lower than with my old 5160s.
I will warn though - watch the heat sink temperature sensor!
They break easy and are hard as hell to find.
-James"

Thanks James. Another 2006 Xserve dual quad-core upgrade report last June used lower clock speed CPUs, but was also very pleased with the results. (Especially at appx $50 total cost.) Much easier to swap CPUs in the Xserves than Mac Pros (especially 2006-2008 Mac Pros).

(* MacPro 1,1 to 2,1 EFI updater (from netkas) to properly ID Quad-Core CPUs and some said it fixed Kernel Panics they had with Quad-Core CPU upgrades in Lion/10.6.8. Mentioned in an earlier post and Mac Pro 1,1 to 2,1 EFI update feedback. Previously (10.5.x) some used "AboutThisMac" util for CPU ID per a 2009 report on 2006 Mac Pro Clovertown Swaps revisited.)
  

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