Quad-Core Nehalem Mac Pros Support 16GB RAM

[polterdice]

From PC Magazine

The Mac Pro finished the Photoshop CS4 test in 1:50 under Mac OS X but took only 1:17 to finish the same tasks under Windows. The performance difference is due to the fact that the Mac version of CS4 can directly address only 3.5GB of the system's memory, while the Windows 64-bit version can access the full 6GB of memory. This can add up to a significant performance benefit.

We are discussing 8vs16vs32 GB RAM, but photoshop can only address 3.5 GB?
On the original release thread someone was discussing the need for more memory when working with multiple RAW images in photoshop. You may want or need more memory, but can't use it.

Of course photoshop performed better under 64 bit windows. CS4 is supported at 32 bit under mac os. For hardware comparison the test should have been run under 32 bit windows, since it would have the same 3.5 ram limitation. Until CS5 is released, photoshop in mac will be at a disadvantage to windows 64 bit; the test is flawed.

And you can use additional ram past 3.5 gb as scratch, so it's not completely useless.

But seriously, people needing more than 4 gb ram are not needing it for photoshop alone.

 

[xbjllb]

Holy crap the 32 GB option is only $1800 at OWC. Meanwhile, Apple sells the same thing for $6100!!! What the hell?!? That'll save me $4.3k!

I am planning a purchase as well. I was wondering if 24GB is faster than 32GB? Is the 4th RAM slot on the Mac Pro buffered or registered, hence slower? And if so how much?

OWC rocks. I've got 4 GB in my iMac that was only supposed to hold 3 GB as far as Apple was concerned.

I highly recommend OWC!

 

[ileneh]

Helpful Blogs

Holy crap the 32 GB option is only $1800 at OWC. Meanwhile, Apple sells the same thing for $6100!!! What the hell?!? That'll save me $4.3k!

I am planning a purchase as well. I was wondering if 24GB is faster than 32GB? Is the 4th RAM slot on the Mac Pro buffered or registered, hence slower? And if so how much?

Hi, I thought I'd post these OWC blog links in an attempt to answer your question.
2009 Mac Pro “Nehalem” Initial Speed Tests: http://blog.macsales.com/672-2009-mac-pro-nehalem-initial-speed-tests

Feed Your Mac Pro More RAM: http://blog.macsales.com/729-feed-your-mac-pro-more-ram

Cautionary Note On Mac Pro Memory: http://blog.macsales.com/547-cautionary-note-on-mac-pro-memory

Hope these help... Not trying to spam!
OWC ilene

 

[Gonk42]

Registered and Unbuffered 4GB RAM modules

I'm currently weighing up the two options of building my own Linux/Windows workstation and buying a Mac Pro with student discount.

I'm curious as to why 4GB unbuffered modules are so much more expensive than 4GB registered modules of otherwise the same spec for example Crucial UK prices (which are presumably much more than say OWC US prices are)

Unbuffered for Mac 12GB (3x4GB) kit of 1066 memory is £1,277:44 inc VAT

whilst registered ram kit is £407.09 both are the same spec apart from being registered or unbuffered and both are 4GB modules.

It is strange because registered memory is normally more expensive.

Also many mother boards (such as Intels) take either registered or unbuffered (but not both) so has anyone tried registered memory in the Mac Pro??

 

[wase4711]

so, does this mean that upgrading to 8 gigs of ram is a waste; 6 gigs is all that a quad core will actually use, since there are only 3 memory channels?

thanks!

 

[AidenShaw]

so, does this mean that upgrading to 8 gigs of ram is a waste; 6 gigs is all that a quad core will actually use, since there are only 3 memory channels?

It means that the first three DIMM slots will run somewhat faster, since they'll be in tri-channel mode.

The fourth slot will be single channel mode.

So you'll have 6 GiB of slightly faster memory plus 2 GiB of slightly slower.

You probably won't notice the slowdown unless you have very memory-intensive programs *and* you actually need 6 GiB or less.

If you need more than 6 GiB, then obviously things will be better with 8.

 

[wase4711]

Thanks Aiden for the clear response!

So, in real world computing, using the machine for everyday tasks, including photoshop, light video processing, and normal office functions like pages/numbers/ and things of that nature, getting 8 gigs of memory should yield slightly better performance than getting 6 gigs?
I still don't understand why Apple didn't make 4 gigs standard, instead of 3 gigs...

 

[AidenShaw]

So, in real world computing, using the machine for everyday tasks, including photoshop, light video processing, and normal office functions like pages/numbers/ and things of that nature, getting 8 gigs of memory should yield slightly better performance than getting 6 gigs?

I can't really estimate how much memory you'd use, but Windows and UNIX systems will use excess memory as a file system cache. Having the two extra gigs for the cache will probably make the system snappier.

I still don't understand why Apple didn't make 4 gigs standard, instead of 3 gigs...

Probably to save a few bucks, increase margin, and be sure that the out-of-the-box system performs best on memory-intensive benchmarks.

 

[wase4711]

Probably to save a few bucks, increase margin, and be sure that the out-of-the-box system performs best on memory-intensive benchmarks.

yeah, I agree with the cost savings part; although adding another gig from the factory would probably have cost Apple about 10 bucks or so..not alot on a $2500.00 machine..as far as the Benchmarks, I guess 6 gigs might give a better number in the memory benchmarks, but I bet in real world testing, like photoshop or archiving, having the 2 extra gigs would make a difference..

I guess I will upgrade to 8 gigs insted of 6; @OWC, the difference between their 6 gig and 8 gig upgrade is about 35 dollars; and, since they will give you some $$$ back if you sell them your "old" memory, the 8 gig upgrade will probably cost around 120 bucks total..blows Apple's $250 dollar 8 gig upgrade away...

Thanks again for the answers to my questions!

EDIT:
Just saw this over at Infoworld...Maybe it makes more sense to just add ram in multiples of 3 insted of 4...6 gigs would keep the clock speed of the RAM at its fastest, since you would only be populating "3" channels instead of "4"

"The strange not-power-of-two memory configuration relates to Nehalem's triple-channel memory controller. Its best performance is derived from attaching three DDR3 DIMMs to each processor. This leaves one or two DIMM sockets vacant, depending on 4 core or 8 core configuration, and there's some controversy over the performance impact of filling them.Due to this architecture change and the nature of DDR3 RAM, the RAM clock runs at 800MHz, 1,066MHz, or 1,333MHz. If the DIMM ranks are populated with a single RDIMM (Registered DIMM) per channel, the highest speed of 1,333MHz is possible. As RAM is added to those "4th" channels, the overall speed drops to 1,066MHz or 800MHz."

 

[midilance]

Seems like they were artificially forcing customers to go for the 8 core by publishing misleading limitations.

As it turns out they forced me to buy the previous generation 8 core and load it up with 12 GB of affordable ram. The advertised 8 GB limit was a deal breaker for me. I need it for music and video production.

 

[brop52]

As it turns out they forced me to buy the previous generation 8 core and load it up with 12 GB of affordable ram. The advertised 8 GB limit was a deal breaker for me. I need it for music and video production.

Apple likes to not be accurate about what the actual maximum is. The Quad Core maxes out at 12GB.

 

[polaris20]

Apple likes to not be accurate about what the actual maximum is. The Quad Core maxes out at 12GB.

As the title says, it maxes out at 16gb

 

[seedster2]

As it turns out they forced me to buy the previous generation 8 core and load it up with 12 GB of affordable ram. The advertised 8 GB limit was a deal breaker for me. I need it for music and video production.

I actually did the same. I bought 2.8 - 8 core with the business discount for my fledgling photography business.

I want this workstation for its expandability. Apple has obviously lost sight of this when the designed the quad

 

[Thomas2006]

I thought the whole point of the MP is that it's supposed to be a HIGH end machine - now you're saying for $2499 you get "low end"?

At that price its certainly not aimed at consumers, why even bother putting out a machine that fails to really make any segment of the market?

This is just a guess, but I think Apple might be turning the low-end Mac Pro into an "xMac". No, it will not be the $1500 model with PCI slots and eSATA that people are asking for since that would cannibalize the Mac mini and iMac sales, as well as, increase expenses associated with producing a new model. Apple will do something simple now that the processors and RAM are on a separate board.

The next update will have the high-end Mac Pro using two 6-core Core i7 processors and the low-end using a singe Core i5 processor, hopefully, with a price drop. The low-end model will still be "too expensive" for those whose processing needs can be met with a dual-core, don't want a built-in monitor, want to add/change video cards, increase storage without cluttering their desktop, and/or need to add an expansion card.