"Subject: Mac Pro 1,1 (8-Core) processor upgrade
Mike, I just finished an 8-core processor upgrade on my 2006 Mac Pro 1,1, from stock X5150's to a pair of pulled X5355's I found on eBay for $57.00. (Ref: Intel X5355 CPU info.) Amazing deal. They've been sitting on my desk for six months and I finally found the time to dive in this week.

I was surprised at how painless this upgrade is and highly recommend it for anyone looking to squeeze more life out of their aging machine. So far I'm ok with stock firmware and I only needed to reset the PRAM after Safari was misbehaving. According to iStat I'm getting temperatures of 28°/32°C idle and 34°/38° during benchmarks, with SMC fan control at 600 rpm.
(BTW: I've not used iStat Menus since v2 (during my 2009 Mac Pro Core Temperature tests w/Audio (bug)) but back then its CPU temperature reported was the heatsink sensor, not the CPU/Cores, so I used Temperature Monitor (free) instead. I wrote them about that back then, but never used later iStat versions.-Mike)

I'm currently running Lion with 16GB memory, an SSD in the optical drive bay for the system drive, ATI 1GB 5770 and a couple PCI Raid controllers for a total of 9 "internal" drives attached. Photoshop, Aperture and FCPX run very nicely. My next step is to procure 8GB more RAM when the deal is right. And if all goes well I'm planning to install Mountain Lion or Mavericks pending research into performance reports.

Geekbench v3 32 bit scores predictably doubled (almost) from 4947 to 9718. Not bad for a 7 year old 50lb machine.

Thanks for keeping this site running for all of us who dare to poke around where we have no business. I've been coming here ever since my first iBook 3GB hard drive upgrade. Always inspiring!
-Rob"

(Links to Mac Pro 1,1 CPU upgrade guides/video are in past upgrade posts like this one.)