Maximum memory for mid 2012 6 core 3.33 ghz Mac Pro?

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Officially your Mac Pro supports 32 GB of memory, but you can install 48 GB of memory without any problem and it will work properly. Apple sets a smaller amount of memory than the memory that the Mac Pro supports, so if you want, you can buy 48 GB of memory and install them

There were few or not at all 16GB DIMMs at the time

There are people running duals with 96GB and for some reason Mac OS had trouble at one point with more than 64 or 80GB, while OS X Server supports full 128GB.

Apple never revises their specs when larger density DIMMs become available. Their specs therefore are always out of date and to be ignored.

SalvatoreF wrote:

Hi,

I see the apple specs for this mac say max memory is 32 GB (4x 8GB), but then OWC has a 48 GB kit for the 6 core, as seen here.

http://eshop.macsales.com/shop/memory/Mac-Pro-Memory#1333-memory

Which is correct?...

There is an additional twist. See http://en.wikipedia.org/wiki/Registered_DIMM to differentiate buffered and unbuffered DIMMs. Getting to 48 GB uses three 16 GB DIMMs but getting to 32 GB requires four DIMMs. The last two DIMMs in that combination share a channel, and according to the linked article, registered DIMMs offer a moderate improvement in performance. The registered DIMMs are here http://eshop.macsales.com/item/OWC/1333D3MPE8GB/.

Nothing is ever simple...

Since Apple will not support these advanced configurations, it is more important than ever that if you go there, you use modules from a Vendor who can provide support for this as well.

"It works in your MAC,

or your money BACK."

Grant Bennet-Alder wrote:

Since Apple will not support these advanced configurations, it is more important than ever that if you go there, you use modules from a Vendor who can provide support for this as well...

Couldn't agree more, which is why the buffered RAM configuration I suggested is what I've got in my Mac Pro right now and OWC was the source.🙂

SalvatoreF wrote:

...It looks like OWC has a 30 day return policy....

It has more than that. As Grant Bennet-Alder says, you want a Vendor who can provide support.

I did, once, have a DIMM generate ECC errors. Called OWC on a Saturday for help. Was emailed a prepaid UPS shipping label within minutes. I shipped the DIMM out Monday, it was received Wednesday, the replacement was shipped out Wednesday and was received and installed Friday. It has been humming along ever since. Wish all my other business dealings went nearly as well.

You are welcome

I just bought a refurbished mid 2012 6 core 3.33GHz Mac Pro from Apple. I want to, for now add two (2) 16GB modules from OWC. Then later add one (1) more 16GB module so I would have a total of 48GB's. Is the consensus among everyone that the RAM that OWC sells (see link below) are the correct ones to buy?

http://eshop.macsales.com/item/Other%20World%20Computing/1333D3X9M032/

I did a live chat with OWC last week and they said to only use the 3 ram slots when installing the 16GB modules. I forgot to ask why added a forth module was a problem.

Oh, I will be running the Maverick OS, and a SSD for my boot drive!

Thanks!

Those two modules should work fine as long as they're not being mixed with anything else (which you're not doing). I'd suggest, however, that you just get all three now since that's the plan eventually. That way, you'll get a matched set. While that isn't essential, a matched set can't hurt. If you wait for the third DIMM, be sure you get the unbuffered module, since that's what those two are, rather than buffered, which won't be compatible.

Using the fourth slot would cause a minor performance hit, because the first three slots each have their own memory bus. The fourth slot shares the bus with the third slot so some latency is added.

So is unbuffered modules what I want and is the correct type to use?

In OWC description of those ram modules, where in there is it indicated that they are unbuffered modules?

I'm on a realy tight budget and right now get three modules are out. I'll keep in mind to make sure to get the unbuffered module.

Thanks,

Either buffered or unbuffered would work (I happen to be using buffered in my Mac Pro), just not together; unbuffered has a slight speed advantage when three slots are used, buffered has the slight advantage when the third memory bus is shared because all four slots are used.

In your case I don't think it will matter because I can't find buffered 16GB DIMMs at OWC, just the 8GB DIMMs. Note the ECC-R designation in the description and the "GB" in the SKU.

Got it! Thanks for helping me out with my confusion about the different ram modules. I think I got it straight!

-Russ