Mac Pro 5,1 and 4,1
Xserve 3,1
Maximum RAM:
56GB in a single-processor Mac Pro using a single-processor-capable Xeon
64GB in a single-processor Mac Pro using a dual-processor-capable Xeon
160GB in a dual-processor Mac Pro
48GB for a single-processor Xserve
96GB in a dual-processor Xserve
For the 4,1 to use Westmere CPUs and run RAM at 1333, it will need the firmware upgrade to 5,1, found here: http://forum.netkas.org/index.php/topic,852.0.html
5,1 Mac Pros shipped with 1333 RAM even when paired with a Nehalem (1066 only) processor. As shipped, the RAM runs at 1066 because of the CPU. However, if you upgrade to a 1333-capable CPU, your RAM will run at 1333 after an NVRAM reset.
Consumer CPUs (i7 9xx) do not support ECC RAM, but Mac Pros 4,1 and 5,1 work fine with non-ECC RAM
Installing a single "Dual Xeon" processor into a single-processor Mac Pro works fine, and actually increases its maximum RAM from 56 to 64GB.
Installing just one single-processor-model CPU into a dual-processor Mac Pro technically works, but this causes an error state with the CPU fan going full blast.
For two CPUs, you must install two "Dual Xeon" processors. You cannot use two i7 or single Xeon processors.
The X#### CPU's tend to have a slightly higher maximum temperature rating than their W#### equivalents.
4,1 dual-processor CPU trays made before May 2009 are problematic with 130W Xeons.
4,1 dual-processor Mac Pro uses a special, "lidless" CPUs (the single-processor models use normal CPUs). This has a different height than the normal CPUs, so if you upgrade a dual-processor 4,1 Mac Pro with different processors, you need to deal with the height difference. There are several ways to do this:
Buy CPUs that someone has already de-lidded.
Buy normal CPUs and de-lid them yourself. Here is thread about delidding yourself and here is a video. (And here is a post warning against delidding yourself.)
Buy normal CPUs and pay for de-lidding service.
Keep the lids on, but be extremely careful about not tightening down the heat sink too much. (If you don't remove the lids it is very easy to tighten down the heat sink screws too much on a CPU that's too large, resulting in damage to the socket, CPU, and/or board.)
Other people have kept the lids on, but added washer stacks (of equivalent height to the lid difference) to where the tightening screws go--this is intended to prevent the heat sink from overtightening and causing damage. Here is an informational washer stack thread, and here is a really good post with pictures and a step-by-step procedure.
If you keep the lids on, the existing heat pad won't reach the heat sink due to the extra height of the lids. You need to make up for this gap by replacing the heat pad with a thicker pad.
The Xserve 3,1 uses lidless CPUs for both single-CPU and double-CPU models. We don't know if the washer-stack trick will work in Xserves as they are physically different than MP, but the other solutions should work.
No, the X5687 (3.6GHz quad-core) and the X5698 (4.4GHz dual-core) do not work in Mac Pros. I don't want to list every CPU that doesn't work with a Mac, but these two are asked about often enough to include here, and they've been verified as not working.
Architecture Cores Grade CPU-Model GHz Turbo RAM Watt MP4,1 MP5,1 XS3,1
Westmere 6 core Dual Xeon X5690 3.46 3.73 1333 130W x* x -
Westmere 6 core Dual Xeon X5680 3.33 3.60 1333 130W x* x -
Westmere 6 core Dual Xeon X5679 3.20 3.60 1066 115W x* x -
Westmere 6 core Dual Xeon X5675 3.06 3.46 1333 95W x* x -
Westmere 6 core Dual Xeon X5670 2.93 3.33 1333 95W x* x -
Westmere 6 core Dual Xeon X5660 2.80 3.20 1333 95W x* x -
Westmere 6 core Dual Xeon X5650 2.66 3.06 1333 95W x* x -
Westmere 6 core Dual Xeon E5649 2.53 2.80 1333 80W x* x -
Westmere 6 core Dual Xeon E5645 2.40 2.67 1333 80W x* x -
Westmere 6 core Dual Xeon L5639 2.13 2.67 1333 60W x* x -
Gulftown 6 core Xeon W3690 3.46 3.73 1333 130W x* x -
Westmere 6 core Xeon W3680 3.33 3.60 1333 130W x* x -
Westmere 6 core Xeon W3670 3.20 3.46 1066 130W x* x -
Gulftown 6 core Consumer i7 990X 3.46 3.73 1333 130W x* x -
Gulftown 6 core Consumer i7 980X 3.33 3.60 1333 130W x* x -
Gulftown 6 core Consumer i7 970 3.20 3.46 1333 130W x* x -
Westmere 4 core Dual Xeon X5687 3.60 3.86 1333 130W - - -
Westmere 4 core Dual Xeon X5677 3.46 3.73 1333 130W x* x -
Westmere 4 core Dual Xeon X5672 3.20 3.60 1333 95W x* x -
Westmere 4 core Dual Xeon X5667 3.06 3.46 1333 95W x* x -
Westmere 4 core Dual Xeon X5647 2.93 3.20 1066 130W x* x -
Westmere 4 core Dual Xeon E5640 2.66 2.93 1066 80W x* x -
Westmere 4 core Dual Xeon E5630 2.53 2.80 1066 80W x* x -
Westmere 4 core Dual Xeon E5620 2.40 2.66 1066 80W x* x -
Westmere 2 core Dual Xeon X5698 4.40 4.54 1333 130W - - -
Nehalem 4 core Dual Xeon W5590 3.33 3.60 1333 130W x x x
Nehalem 4 core Dual Xeon W5580 3.20 3.46 1333 130W x x -
Nehalem 4 core Dual Xeon X5570 2.93 3.33 1333 95W x x x
Nehalem 4 core Dual Xeon X5560 2.80 3.20 1333 95W x x -
Nehalem 4 core Dual Xeon X5550 2.66 3.06 1333 95W x x x
Nehalem 4 core Dual Xeon E5540 2.53 2.80 1066 80W x x -
Nehalem 4 core Dual Xeon E5530 2.40 2.66 1066 80W x x -
Nehalem 4 core Dual Xeon E5520 2.26 2.53 1066 80W x x x
Nehalem 4 core Xeon W3580 3.33 3.60 1333 130W x x -
Nehalem 4 core Xeon W3570 3.20 3.46 1333 130W x x -
Nehalem 4 core Xeon W3565 3.20 3.46 1066 130W x x -
Nehalem 4 core Xeon W3540 2.93 3.20 1066 130W x x -
Nehalem 4 core Xeon W3530 2.80 3.06 1066 130W x x -
Nehalem 4 core Xeon W3520 2.66 2.93 1066 130W x x -
Nehalem 4 core Consumer i7 975 3.33 3.60 1333 130W x x -
Nehalem 4 core Consumer i7 965 3.20 3.46 1066 130W x** x** -
Nehalem 4 core Consumer i7 960 3.20 3.46 1066 130W x x -
Nehalem 4 core Consumer i7 950 3.06 3.33 1066 130W x x -
Nehalem 4 core Consumer i7 940 2.93 3.20 1066 130W x** x** -
Nehalem 4 core Consumer i7 930 2.80 3.06 1066 130W x x -
Nehalem 4 core Consumer i7 920 2.66 2.93 1066 130W x** x** -
* Requires 4,1 to 5,1 firmware upgrade
** Some or all steppings of these CPUs don't work with certain newer Mac Pro firmware versions applied by High Sierra 10.13.5 updates and newer. See this thread. The thread also has a method for adding the code back to make the CPUs compatible again.
Note: Reports of GAINESTOWN (Xeon 5500-series) processors in Mojave experiencing audio related issues. See this thread for more information.