I have a MacPro5,1 (2010) with a 4-Core 3.2 GHz (W3565) and 12 GB RAM (3x4GB ECC 1066 MHz; 1 slot free).

Would this be possible to possible to purchase 2 X5690 (3.46GHz/6-core/12MB/130W) processors to upgrade this or would I need a new tray + heatsink and some firmware update?

Also, would the upgrade then also accept a 128 GB memory upgrade (via 8x16 GB; 1333MHZ DDR3 PC3-10600 Reg ECC Low Voltage DIMM)?

1 Answer 1


You'd need a new daughterboard & both heatsinks, at least - the single & dual CPU boards are physically different & the singles have larger heatsinks which won't fit the duals.

picture from OWC

Changing the board also gives you 4 more RAM slots & a potential maximum of 128GB RAM, if you are running Mavericks 10.9 or later.
With earlier OSes, though it will take 128GB RAM [8x16GB in dual channel], OS X cannot use it all - it only supports a maximum of 96 GB [6x16 in triple channel].
Bootcamp into Windows & all 128 is a possibility.

The 5,1 should already have the firmware necessary to support the Westmere processors, the update is only necessary for the 2009 4,1.

BTW, if you are considering doing this yourself, be aware that standard off-the-shelf CPUs are expected to go in PCs not Macs & have lids. The ones for Mac are lidless.
You can make the lidded processors fit, but it's fiddly [& would need an entire answer in itself]

Refs: Everymac, MacSales, OWC & being the owner of a similarly upgraded 4,1

  • I'm just curious about your comment that OS X only supports a maximum of 96 GB of RAM. Is this based on a particular version of OS X? I ask because Apple states, "OS X provides approximately 18 exabytes of addressable space for 64-bit processes". See the second paragraph.
    – Monomeeth
    Nov 14, 2016 at 8:40
  • It's always been the "word on the street". EveryMac & OWC are my usual sources for this type of thing - blog.macsales.com/… - & people such as the builder of my own machine seem to agree that 96 is maximum. I only have 8GB sticks here so there's no way I can test the theory. It might also be that this has changed in recent OSes; this data is all from 2012 10.7. The page you ref is also concerned with VM, maybe physical access is different?
    – Tetsujin
    Nov 14, 2016 at 8:44
  • Okay, thanks. I think this has indeed changed in recent OSes, although I'm not entirely sure when. Also, the Mac Pro (Late 2013) actually supports 128 GB RAM (although Apple only officially supports 64 GB RAM). So as a minimum we have a real world example of more than 96GB RAM being supported.
    – Monomeeth
    Nov 14, 2016 at 8:50
  • Ahh... I went through OWC's memory configurator & found this - **Mac OS X versions prior to 10.9 Mavericks are unable to utilize more then 96GB RAM due to an operating system limitation. 128GB can be fully utilized by a 2009-2010 Mac Pro if running 10.9 Mavericks or later, Bootcamp with 64-bit versions of Windows XP and later as well as with 64-bit versions of Linux. So my info is now out of date
    – Tetsujin
    Nov 14, 2016 at 8:51
  • 2
    So I managed to install 2 X5690 processors with the heat spreader / lid intact, but I had to build up the heatsink where it makes contact with the chips on the edge of each. Gotta be real careful not to tighten the heatsinks down very much. Got the dreaded blinking SIL light in front and had to ease it back on the tightness. The Compaq server RAM was initially only recognizing at 1066 MHz, but after resetting the pram (just the nv didn't do the trick) 3 times via cmd-option-p-r, the system restarted with 1333 MHz. So all of this worked out on a 2009 vs my 2010! Very happy.
    – ylluminate
    Nov 18, 2016 at 16:09

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