Ram question Mac Pro 2009 5,1

The RAM spec has nothing to do with Mac, as long as the spec is correct, it will work.

You need either PC3-8500 or PC3-10600 for the Mac Pros. That RAM you linked to looks to be (if the pic is correct) PC3-10600R which means it's registered memory (mainly used in servers). I think it might work in the Mac Pro but someone else will have to confirm. I have never dealt with registered DIMMs before in a Mac.

Mac specific DIMMs are not required for Macs. 3rd party RAM has always been pretty well supported in New World ROM Macs (minus the original iMac and a few select PPC machines). Most of the RAM I have purchased used from eBay has never been made for the Mac and it works fine.

Oh, and I'd make sure to get ECC RAM. It's not required, but Apple recommends it and that's what the machines would have shipped with originally.

that memory will work...but you will not be able to match registered ram with unregistered

buster84 said:

I'm guess that the original ram that comes from apple isn't Registered which means that i won't be able to mix them, but that would fine since it would replace all slots anyways.

Click to expand...

The RAM isn't registered, but as a general rule of thumb I don't mix RAM speeds and brands if I can help it, particularly RAM speeds. If that's the stock 6GB and it was originally a 4,1, then it would be PC3-8500 (1066MHz) memory. With the right 5,1 processor, it will take full advantage of PC3-10600 (1333MHz) memory.

My recommendation is to get all new PC3-10600 DIMMs if you can. That's what I did for my 4,1->5,1 and it works like a champ.

That RAM will almost certainly work, while I've not used that exact RAM, I have used many different brands of PC3-10600R RAM and yet to have any compatibility issues. As others mentioned, the 2009 Mac Pro comes with PC3-8500E RAM, and you cannot mix it, so you'll almost certainly need to remove any RAM you may already have installed.

You can probably find it a little cheaper if you look. For the set of 8x4GB expect to pay around $120. While any 4GB PC3-10600R RAM would work just fine, what I usually tell people to search for when looking for RAM would be:
'PC3-10600R 4GB 16GB'
This usually brings up quite a few good results. The reason to search for a set of 4 is that most of the RAM comes from servers, and very few servers have 8 slots, so it's not as common to find a lot of 8, lots of 4 are much more common, and often end up being a little cheaper.

As you supposed in the OP, RAM that works on any Nehalem/Westmere Xeon should work in a MP 4.1/5.1. That's due to the fact that the memory controller is integrated into these CPUs, so it's the same across all Xeon based machines. Registered RAM should work but has a small performance penalty compared to unbuffered memory. Mixing different types of RAM is generally a bad idea as it has an unpredictable and possibly big impact on memory performance. On dual-CPU it's also recommended that both CPUs have the same memory configuration for best performance.

For those interested, I've written some tips on RAM configuration based on an IBM article about Westmere Xeons here.