Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Confirmation of Westmere Memory Config

xgman

xgman

macrumors 603
Original poster
Aug 6, 2007
5,672
1,378
eidt: the 6 core is on a workstation board it appears and not a server board. The server boards may or may not be dual channel capable but the 4 slot boards are 3 + 1, so disregard the rest of this post. Sorry about the misinfo. If only Apple had spelled this out for us. . . . .


I spoke with the Micron engineer who personally tested the 4, 6 and 12 core 2010 mac pros on August 9th with regard to memory compatibility.
After a long conversation and some additional research he confirmed that in fact the six core Westmere Mac Pro is a dual channel memory system (integrated in the chipset) and NOT a triple channel system like the 2009 Nehalem chipset Mac Pro systems were. Therefore the best way to populate the 4 slots is to populate them all with identical memory which will run in effect in dual channel mode.

In addition. He stated that he in fact tested 8GB sticks of 1333 ram in the six core system and it did recognize and run the 8GB sticks. In fact Crucial has these 8GB sticks (albeit very expensive) listed now on their site as compatible with the 2010 Mac Pros.

I certainly wish I had this info when I placed my memory order with Transintl. Nevertheless, it seems to indicate that the max amount of ram for the six core is looking much better indeed. By the way, the board is a derivative of the Intel 5520 for anyone who is interested.

"Unlike Core i7, however, mainstream desktop/mobile Westmere chips will not feature a QPI bus or a triple-channel memory controller. Rather, we'll revert to a dual-channel controller and have no QPI clock to worry about"
 
S

skiffx

macrumors 6502a
Feb 5, 2008
681
10
xgman said:
I forwarded this to him. he is going to test this as soon as a system arrives.
Click to expand...

I just cancelled my order of 4x4 and replaced it with 3x4gb thinking it was triple, so this is 100% confirmed that it runs as dual channel and 4x4 would run faster?!
 
xgman

xgman

macrumors 603
Original poster
Aug 6, 2007
5,672
1,378
skiffx said:
I just cancelled my order of 4x4 and replaced it with 3x4gb thinking it was triple, so this is 100% confirmed that it runs as dual channel and 4x4 would run faster?!
Click to expand...

Yes. Everyone wrongly assumed it would be as the 2009. (well most everyone )
 
L

lssmit02

macrumors 6502
Mar 25, 2004
400
37
I'm not sure this is right. According to Apple, the chip in the six core is the W3680. According to Intel's site,
# of Memory Channels 3
Click to expand...
. Link. I assume this means it's triple channel memory. Note also, Intel's site also says the maximum amount of memory is 24GB.
 
xgman

xgman

macrumors 603
Original poster
Aug 6, 2007
5,672
1,378
lssmit02 said:
I'm not sure this is right. According to Apple, the chip in the six core is the W3680. According to Intel's site, . Link. I assume this means it's triple channel memory. Note also, Intel's site also says the maximum amount of memory is 24GB.
Click to expand...


Westmere is based on dual channel. Not sure what that is referring to above.

Westmere’s memory controller can drive two DIMMs per channel at the full 1.33GT/s. Current Nehalem systems (and most AMD systems) run two DIMMs per channel at reduced bandwidth; Nehalem’s memory controller operates two DIMMs per channel at 1.06GT/s, sacrificing about 20% of the bandwidth.

the Nehalem core supported three channels of DDR3 memory, but you could only acheive maximum speed (1333mhz) with a single DDR3 DIMM per channel. With Westmere, Intel has tweaked the memory controller for performance, so now you can still get to that 1333mhz number with two DIMMs installed per channel. An end user can now buy cheaper, lower density DIMMs without fear of performance degradation. The new and improved memory controller also supports new low-voltage DDR3 memory modules.
 
D

deconstruct60

macrumors G5
Mar 10, 2009
12,302
3,895
xgman said:
After a long conversation and some additional research he confirmed that in fact the six core Westmere Mac Pro is a dual channel memory system (integrated in the chipset) and NOT a triple channel system like the 2009 Nehalem chipset Mac Pro systems were.
Click to expand...

Err the Nehalem 2009 also is dual interleave mode if fill 4 slots. If these experiements were in filling 4 slots then this is no suprise, nor an confirmation that it solely runs in dual interleave mode in all contexts. ( Very unlikely that this interleave mode does not change as the configurations are changed. )



Therefore the best way to populate the 4 slots is to populate them all with identical memory which will run in effect in dual channel mode.
Click to expand...

The problem with 8GB DIMMs and that approach is that you end up with 32GB. The spec sheets on the 3680 say that it tops out at 24GB.

http://ark.intel.com/Product.aspx?id=47917&processor=W3680&spec-codes=SLBV2
 
xgman

xgman

macrumors 603
Original poster
Aug 6, 2007
5,672
1,378
To be honest we need to know exactly which model Intel motherboard this is based on and is it in fact the W3680 or the X5680. The resulting answer is quite different. The W3680 is a workstation processor that fits on theWX58EP Intel board and does have triple channel 3 slots plus on extra slot.

The X5680 fits on a server board, like the Intel 5520 and they use dual channel.

So which is it?
 
T

trankdart

macrumors member
Jul 28, 2010
60
0
Los Angeles, CA, USA
So the 2010 Nehalem-based quads use a different chipset? Different mobo? They're still Nehalems but they have fewer memory controllers than the Nehalems in the 2009 version? Or does the Westmere use two channels while the 2010 Nehalems still use 3?

I would bet my house that the Micron engineer is mistaken. I believe Apple is using the same motherboard with the same or nearly the same chipset as last year, and that the Westmere has the 3 memory channels that Intel most unambiguously says it does, just like the Nehalem. I think the Westmere goes into the same socket on the same board with the same chipset as the Nehalems (it certainly does in my Linux server), and that all of them talk directly to the main memory subsystem with their 3 memory controllers independently of the chipset anyway.

Unless there is a technical document from Apple or Intel confirming what the Micron employee said, I see no reason to believe it. It contradicts all the other available evidence.

TD
 
Umbongo

Umbongo

macrumors 601
Sep 14, 2006
4,934
55
England
xgman said:
To be honest we need to know exactly which model Intel motherboard this is based on and is it in fact the W3680 or the X5680. The resulting answer is quite different. The W3680 is a workstation processor that fits on theWX58EP Intel board and does have triple channel 3 slots plus on extra slot.

The X5680 fits on a server board, like the Intel 5520 and they use dual channel.

So which is it?
Click to expand...

5520 is triple channel with two sockets each with their own memory.
 
VirtualRain

VirtualRain

macrumors 603
Aug 1, 2008
6,304
118
Vancouver, BC
xgman said:
I spoke with the Micron engineer who personally tested the 4, 6 and 12 core 2010 mac pros on August 9th with regard to memory compatibility.
After a long conversation and some additional research he confirmed that in fact the six core Westmere Mac Pro is a dual channel memory system (integrated in the chipset)
Click to expand...

Ok, that makes no sense at all. The Memory Controller for Nehalem/Westmere is on the CPU die, not on the chipset... so you've lost me here.

Also, most certainly, the memory controller on Westmere is the same as on Nehalem... that is... a tri-channel controller.

I suppose it might be possible, that the 2010 CPU daughter card is only using 128 bits of the 192 bit memory bus with two DIMM sockets wired to each of two 64 bit channels, but that would have required a completely unnecessary redesign of the CPU daughter card to provide down-graded performance. Very unlikely Apple did this.

xgman said:
In addition. He stated that he in fact tested 8GB sticks of 1333 ram in the six core system and it did recognize and run the 8GB sticks. In fact Crucial has these 8GB sticks (albeit very expensive) listed now on their site as compatible with the 2010 Mac Pros.

I certainly wish I had this info when I placed my memory order with Transintl. Nevertheless, it seems to indicate that the max amount of ram for the six core is looking much better indeed. By the way, the board is a derivative of the Intel 5520 for anyone who is interested.

"Unlike Core i7, however, mainstream desktop/mobile Westmere chips will not feature a QPI bus or a triple-channel memory controller. Rather, we'll revert to a dual-channel controller and have no QPI clock to worry about"
Click to expand...

This is complete nonsense... where did this quote come from? EDIT: I see this came from the Techgage page which is in reference to Arrandale and Clarkdale.

Of course all Nehalem/Westmere CPU's have a QPI bus to communicate with the X58 chipset.
 
xgman

xgman

macrumors 603
Original poster
Aug 6, 2007
5,672
1,378
lssmit02 said:
According to Apple it's the W3680 for the six core Mac Pro.
Click to expand...

Should have merged these threads:

the W3680 is a workstation processor, not a server processor and would go into a Intel WX58EP motherboard. Now, I can't confirm that is the board the Apple is based on, but no server board is listed as compatible with the W3680. That means our original thoughts on the 3 channels are correct. I am going to test 8gb x 3 as soon as I can. Sorry for any confusion. Apple could have given us a memory config lesson on this but .. .
 
D

deconstruct60

macrumors G5
Mar 10, 2009
12,302
3,895
xgman said:
Westmere is based on dual channel. Not sure what that is referring to above.
....
the Nehalem core supported three channels of DDR3 memory, but you could only acheive maximum speed (1333mhz) with a single DDR3 DIMM per channel. With Westmere, Intel has tweaked the memory controller for performance, so now you can still get to that 1333mhz number with two DIMMs installed per channel.
Click to expand...

Self contradictory statements. In the first there are only two. Later Westmere is Nehalem with an update so that can run two banks of DIMMs at the higher speed. The latter is true. The former... have no idea where it comes from.

Running both bank 1 and 2 at 1333MHz doesn't necessarily make Westmere "dual channel". That would be one way of implementing it but likely kept the physical channel the same, just improvements on processing the signal quality. Each channel can support up to 3 DIMMs. Most designs conserve board space though and leave the 3rd off. (It additionally drops the memory transfer speed even more for both new and tweaked versions. )
 
xgman

xgman

macrumors 603
Original poster
Aug 6, 2007
5,672
1,378
There actually are dual channel memory based server boards and triple channel based workstation boards both taking different westmere processors and therein lies the confusion. Bottom line is Apple should have spelled all this out in detail. How else are we to decide how to configure the optimal size, number of sticks and speed of the ram? Anyway, sorry again for any confusion I may have caused.
 
S

sirnh

macrumors regular
Aug 16, 2006
105
0
xgman said:
There actually are dual channel memory based server boards and triple channel based workstation boards both taking different westmere processors and therein lies the confusion. Bottom line is Apple should have spelled all this out in detail. How else are we to decide how to configure the optimal size, number of sticks and speed of the ram? Anyway, sorry again for any confusion I may have caused.
Click to expand...

The memory controller is in the the processor package. I think a board vendor would have to go out of their way to limit a Westmere to just dual channel, mainly by providing just 2 slots. The controller will default to triple channel if 3 modules are installed, and dual channel if 2 or 4 modules are installed.
 
xgman

xgman

macrumors 603
Original poster
Aug 6, 2007
5,672
1,378
G

glassbathroom

macrumors 6502
Aug 6, 2004
362
0
London
Now I am really confused. I am guessing we are not going to finally resolve this 100% until someone has a new MP and has tested it. Is this correct?
 
T

trankdart

macrumors member
Jul 28, 2010
60
0
Los Angeles, CA, USA
I agree there remain unanswered questions, and I don't think anybody here is going to do the test that resolves them. And I don't think a Kingston or Crucial employee who gets happier the more memory sticks get installed is a reliable source for answers (except maybe whether 8GB sticks work at all).

There are some questions only Apple can answer. Intel can't even answer them. Example: on a DP machine, how does the Nehalem NUMA architecture play into the whole memory channel latency story? 2 channels, 3 channels or no channels, how much latency is added if one CPU has to go over the interprocessor QPI link to get data in the memory attached to the other one? That depends to some extent on how (and whether) the operating system deals with the tricky fact of NUMA.

I think it's going to take anandtech or somebody like that to come up with some meaningful numbers. It would be nice if Intel would just answer, completely and in plain language, the simpler questions, like PRECISELY what happens when you populate that 4th slot?
 
D

dhro1

macrumors newbie
Apr 20, 2010
23
0
trankdart said:
I I don't think a Kingston or Crucial employee who gets happier the more memory sticks get installed is a reliable source for answers
Click to expand...

I fully agree with this. I enquired at crucial UK about the possibility of a compatible 3x4GB set for the six core and the response was:

Thanks for your e-mail.

This system can support up to 16GB over the four slots (4GB per slot) and the system uses Dual Channel functionality so we would recommend installing matching pairs.

Please also bear in mind that a 32-bit Operating System will only see and utilise around 3GB when more is installed.

You can order the compatible 4GB memory modules at the following link:

http://www.crucial.com/uk/store/partspecs.aspx?imodule=CT51264BA1339

Or you can order the 2GB memory modules here:

http://www.crucial.com/uk/store/partspecs.aspx?imodule=CT25664BA1067

Or you can order the 12GB kit 3x4GB modules here:

http://www.crucial.com/uk/store/partspecs.aspx?IMODULE=CT3KIT51264BA1339

Please let us know if we can offer additional assistance or advice.

This directly contradicts their claim of a maximum of 32GB and the 8GB sticks they sell in pairs only on their compatibility page. While the memory they recommend is non-ECC and I'm sure OS X SL is predominantly 64 bit and has no problems addressing more than 3GB.
 
xgman

xgman

macrumors 603
Original poster
Aug 6, 2007
5,672
1,378
I spoke with a high level apple rep last night and they agreed that apple should have posted a full description. Of the memory channel setup for each version of the new Mac pro. They failed to understand the "pro" computer needs "pro" explanations critical to how buyers will configure their orders for optimal performance. Hopefully they will update the spec chart. Sorry for the bad info previously posted on this. It has been an eye opening lesson. Hopefully I will be able to test some 8gb modules on this next week, but there is no guaranty they will work.
 
mattmower

mattmower

macrumors regular
Aug 12, 2010
116
18
Berkshire, UK
xgman said:
I spoke with a high level apple rep last night and they agreed that apple should have posted a full description. Of the memory channel setup for each version of the new Mac pro. They failed to understand the "pro" computer needs "pro" explanations critical to how buyers will configure their orders for optimal performance. Hopefully they will update the spec chart. Sorry for the bad info previously posted on this. It has been an eye opening lesson. Hopefully I will be able to test some 8gb modules on this next week, but there is no guaranty they will work.
Click to expand...

A small amount of extra information, I emailed Crucial in the UK about their 8GB part and whether they had tested on pre-release units and they responded:

>Thanks for your email. I can confirm that the 2010 6 Core Mac Pro will
>support 8GB per slot for a 32GB capacity. We have indeed tested the 8GB
>modules to work on pre release units of this model and we guarantee them
>to be compatible.

Matt
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom