MacVidCards

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Nov 17, 2008
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Popular myth has been 48GB.

Problem with "Copy & Paste" knowledge, it often isn't very knowledgeable.

3 @ 16GB and 1 @ 8 GB gives you 56GB.

Still waiting for working 32GB modules for these.

Someone needs to make this post outdated.
 
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Umbongo

macrumors 601
Sep 14, 2006
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Popular myth has been 48GB.

Problem with "Copy & Paste" knowledge, it often isn't very knowledgeable.

3 @ 16GB and 1 @ 8 GB gives you 56GB.

Still waiting for working 32GB modules for these.

Someone needs to make this post outdated.

Which DIMMS did you use? I'd speculated previously if it was due to people using quad-ranked DIMMS and the system not liking 8 ranks on a channel, or playing up because of how it interleaves with 4 DIMMs.

If it wasn't a capacity issue then the 32GB RDIMMs being olf as Mac Pro compatible (not 32GB LR-DIMMS) may well work.
 
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DeltaMac

macrumors G4
Jul 30, 2003
11,110
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Delaware

Yep, you're missing that the 4/6 core MacPro has only 4 RAM slots.
Limited to 3x16 GB sticks (apparently will also work adding an 8 GB stick to the 4th slot - Maxing out at 56 GB with 4 slots available)

8/12 core MP has 2 sets of RAM slots (8 slots available)
It has no limitation for maxing all 8 slots, 8 x 16 GB for 128 GB
 
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h9826790

macrumors P6
Apr 3, 2014
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Hong Kong
Ah.. I am quite sure the 4th slot in the single CPU 2009 Mac Pro is actually OK for another 16G of RAM, make it 64G max at this moment, but just not optimum for performance.
 
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Prince134

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Aug 17, 2010
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Ah.. I am quite sure the 4th slot in the single CPU 2009 Mac Pro is actually OK for another 16G of RAM, make it 64G max at this moment, but just not optimum for performance.

OK

I have both 12 core and 6 core 09-12 Mac Pro. I did it for myself and concluded that the Max Ram for 6 Core is 64GB (4x16gb) for dual pqi CPUs which means X series Xeon, i.e. X5670, x5690. I used X5670 and concluded the answer. For W series, w3680, w3690 or i7980X, the max Ram is 48GB (3x16gb). Put 64GB won't boot in my W3680 machine.

I remember some one in another thread mentioned "perhaps" have OWC test it with X series Xeon for 64GB on single processor Mac Pro. I am not OWC, but I did the experiment here. My conclusion is 64GB with X...xeon, 48GB with W...xeon or i7 (56GB by OP did with 8GB on 4th slot).

Given the result, it's weird why is that? But the truth is truth here. So people have single processor 09/12 Mac Pro can have 64GB (4x16gb), but remember to upgrade X series instead of W if you really want that 64GB psychologically.
 
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crjackson2134

macrumors 601
Mar 6, 2013
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Thanks, this is good stuff. When the Apple Care runs out on my 5.1 6 core, I'll look for the slightly faster 3.4GHz X series processor and grab another 16GB stick for the 4th slot.
 
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MacVidCards

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Yes, this is tested with W3690.

If all 4 sticks of 16gb are present it locks during boot with black screen with sparkly white Apple. May get a x56xx and verify this other theory.
 
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666sheep

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Dec 7, 2009
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64GB works OK in single

I can confirm that 4x 16GB works in single CPU 5,1 using Dual QPI CPU.
I tested X5650, because I only own these ATM.
In mine memory runs @800 MHz, because currently I have 3 sticks of 1066 and 3 sticks of 1600 RDIMMs, so I had to combine them in one or another way and it always yields 800 MHz.

That's only for testing purposes, because 48GB is enough for my use and I prefer to have triple channel over dual channel mode.
 

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MacVidCards

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Confirming 64GB running at 1333 Mhz in Single Core

Looks like a good reason to buy "X" series Xeons with Dual QPI link.

The 4,1 and 5,1 continue to amaze.
 

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funwithdesign

macrumors regular
Dec 9, 2011
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What needs to be determined is this.

The W/X refers to the TDP of the chip not the QPI. The 5 or 3 is what you need to look at.

I have a W5590 which is the Dual Quad 3.33. I'm assuming that because it's a dual chip that it probably can run 64GB, but who knows.
 
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flowrider

macrumors 604
Nov 23, 2012
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The W/X refers to the TDP of the chip not the QPI. The 5 or 3 is what you need to look at.

Not really, the Alpha Designations mean:

E = Enterprise
W = Workstation
X = Extra or High Speed

At least that's what it meant for the 35xx and 55xx series.

For the 36xx and 56xx, Intel seems to have abandoned the W designation of the 56xx series, leaving it for the 56xx series use only.

Lou
 
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funwithdesign

macrumors regular
Dec 9, 2011
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Yes you are correct. Some of the 'X' chips do have the 130W TDP.

It is not however an indicator of dual vs single CPU.

Not really, the Alpha Designations mean:

E = Enterprise
W = Workstation
X = Extra or High Speed

At least that's what it meant for the 35xx and 55xx series.

For the 36xx and 56xx, Intel seems to have abandoned the W designation of the 56xx series, leaving it for the 56xx series use only.

Lou
 
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flowrider

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Nov 23, 2012
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It is not however an indicator of dual vs single CPU.

I agree, I never said it was a single/dual indicator. The single/dual indicator is the lead numeric either a 3 or 5. However, Dual CPU chips can be used in single CPU applications, not visa versa.

Lou
 
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funwithdesign

macrumors regular
Dec 9, 2011
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Oh I know. I was more referring to Prince134's comment above and others regarding QPI and W/X chips.

To be clear for new folks reading this, a W chip does not mean Single CPU.

I agree, I never said it was a single/dual indicator. The single/dual indicator is the lead numeric either a 3 or 5. However, Dual CPU chips can be used in single CPU applications, not visa versa.

Lou
 
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macuser453787

macrumors 6502a
May 19, 2012
578
151
Galatians 3:13-14
Seeing as how the conversation on this thread has sparked back up, I'll ask my question again:

With a W3680, will upgrading to 56GB RAM hobble the RAM speed similar to the above example (X5650 with 64GB)?

I really want to know because I'd like to get the extra 8GB module if it won't affect the RAM speed.

:)
 
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666sheep

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Dec 7, 2009
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If you'd use dual rank sticks it won't, but you'll lose triple channel. In 56GB config (3x 16 + 1x 8) memory will run in single channel mode.
 
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Korican100

macrumors 65816
Oct 9, 2012
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Oh I see. Well then if I gain an extra 8GB at the expense of overall performance, I'd rather stick with 48GB in triple channel. Thanks for your help! :)

Can I ask what do you do, where you'd actually need those extra 8 gb of ram -- where 48gb isn't quite cutting it?

edit: I just realized how seemingly rude my comment seems lol. I don't mean any offense by it, I just am curious. I would like to expand my ram also, but im stuck at 24gb with 3x8 chips
 
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macuser453787

macrumors 6502a
May 19, 2012
578
151
Galatians 3:13-14
Can I ask what do you do, where you'd actually need those extra 8 gb of ram -- where 48gb isn't quite cutting it?

edit: I just realized how seemingly rude my comment seems lol. I don't mean any offense by it, I just am curious. I would like to expand my ram also, but im stuck at 24gb with 3x8 chips

No problem! Actually I suppose that 48GB will probably do very well. I'm doing some upgrading for video editing and I just thought why not since it's an extra 8GB. :)
 
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stockholm80

macrumors member
Jul 12, 2013
57
11
Los Angeles
Reviving an old thread here...

In a 56 GB config (3x 16 + 1x 8), could anyone recommend a memory brand that they have confirmed is working?

I tried OWC RAM in this configuration on my Mac Pro 6-core W3690 and it is not working. My system will not boot.
 
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