MacPro5,1 RAM configuration question

whwang

macrumors regular
Original poster
Dec 18, 2009
130
69
Hi,

I have a 2010 MacPro5,1, with six 16GB RAM modules in it. Recently I found one of them is broken, undetectable by the system. OWC told me that it’s better to return all the six modules and get them replaced together, to ensure they are mateched.

I plan to wait until my iMacPro arrives and then return the RAM for replacement. This is because if I return them now, I will be left with only 24GB of RAM (those originally came with the MacPro) for a substantial period. And this won’t be enough.

So in short, I will keep running my MacPro for a while with the five good 16GB modules. My question is, should I install all five of them, or just four (two for each CPU)? 80GB of RAM and 64GB aren’t that different for me, at least for a while. Will there be any issue if the two CPUs have different amounts of RAM modules installed for them?

Thanks.
 

h9826790

macrumors G5
Apr 3, 2014
14,146
6,782
Hong Kong
Hi,

I have a 2010 MacPro5,1, with six 16GB RAM modules in it. Recently I found one of them is broken, undetectable by the system. OWC told me that it’s better to return all the six modules and get them replaced together, to ensure they are mateched.

I plan to wait until my iMacPro arrives and then return the RAM for replacement. This is because if I return them now, I will be left with only 24GB of RAM (those originally came with the MacPro) for a substantial period. And this won’t be enough.

So in short, I will keep running my MacPro for a while with the five good 16GB modules. My question is, should I install all five of them, or just four (two for each CPU)? 80GB of RAM and 64GB aren’t that different for me, at least for a while. Will there be any issue if the two CPUs have different amounts of RAM modules installed for them?

Thanks.
80GB should be fine
 

bsbeamer

macrumors 68040
Sep 19, 2012
3,654
1,930
I do remember YEARS ago that it was recommended to keep the same number of sticks per CPU for a dual processor. Unsure if that's still the case, but keep in mind in case you do run into any problems. (Doubt there will be any major issues.)

If you see a red light through the front grates it means there's an error. Had a bad stick that I was unaware of for at least a few weeks...
 

whwang

macrumors regular
Original poster
Dec 18, 2009
130
69
Thanks. I even remember for this generation of MacPro, three RAM modules per CPU can be faster than four or two. But I don’t know exactly why. I think my memory about this makes me wonder if I should install three for one CPU and two for the other. What will happen if the two CPU/RAM combinations are running at slightly different speeds? Can this drag the overall performance down?
 

bsbeamer

macrumors 68040
Sep 19, 2012
3,654
1,930
Thanks. I even remember for this generation of MacPro, three RAM modules per CPU can be faster than four or two. But I don’t know exactly why. I think my memory about this makes me wonder if I should install three for one CPU and two for the other. What will happen if the two CPU/RAM combinations are running at slightly different speeds? Can this drag the overall performance down?
In theory, it could cause a bottleneck which would slow the system down. That would likely require both processors being actively under load and unable to "keep up" at the same speed, which would also require your given application(s) actually utlizing dual-CPUs properly. Hard to know for sure if this will happen or not.

I know for sure the 6-core single processor Xeon MacPro's are at 48GB RAM limit, which is a limitation of the CPU itself. In a single configuration, this is not a problem. Personally, I would go with two & two.
 

pl1984

Suspended
Oct 31, 2017
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2,642
Thanks. I even remember for this generation of MacPro, three RAM modules per CPU can be faster than four or two. But I don’t know exactly why. I think my memory about this makes me wonder if I should install three for one CPU and two for the other. What will happen if the two CPU/RAM combinations are running at slightly different speeds? Can this drag the overall performance down?
The processors use triple memory channels meaning it can access three modules at a time. Thus a three module configuration is optimized to the processor.
 

bsbeamer

macrumors 68040
Sep 19, 2012
3,654
1,930
The max is 56GB (3x16+8) at this moment, not 48GB. Also no one try the 32GB DIMM yet, those hex core processor may able to boot with more than 56GB RAM.
Have you run 3x16 + 8 in your system yet?

FYI - this is specifically posted at OWC for their RAM modules:
OWC 16GB modules require that all installed modules be of the same p/n OWC 16GB modules. Other existing Apple or 3rd party 1GB, 2GB, 4GB and 8GB modules are not supported for use with these kits and need to be removed when these modules are added.

Have not seen 32GB modules stocked anywhere that include MacPro5,1 compatibility. There's a few off-brand names on Amazon, but prices are too steep for an experiment.
 

h9826790

macrumors G5
Apr 3, 2014
14,146
6,782
Hong Kong
Have you run 3x16 + 8 in your system yet?

FYI - this is specifically posted at OWC for their RAM modules:
OWC 16GB modules require that all installed modules be of the same p/n OWC 16GB modules. Other existing Apple or 3rd party 1GB, 2GB, 4GB and 8GB modules are not supported for use with these kits and need to be removed when these modules are added.

Have not seen 32GB modules stocked anywhere that include MacPro5,1 compatibility. There's a few off-brand names on Amazon, but prices are too steep for an experiment.
It's been tested by members here.

Dual processors model can go up to 160GB RAM (5x32).

Anyway, none of Apple, Intel, and OWC get this limitation right. And I may treat Apple or Intel's limitation as the official information. But OWC's info means absolutely nothing. Their 16GB DRIMM may not work with other size DIMM is because they never told you RDIMM cannot work with UDIMM, and they sell 16G RDIMM, but 1,2,4,8 UDIMM.
 

kohlson

macrumors 68020
Apr 23, 2010
2,329
691
Optimal *memory* speed comes from 3 sticks per CPU, installed correctly. IIRC, there is a 5-7% performance penalty (memory, not overall throughput) for installing 4 sticks per CPU. The presumption here is that the user installs exactly the amount of memory needed (remember, these are server parts). But if the workload requires more memory than is available from the 3 sticks, adding a 4th stick is desirable over hitting swap.
In my observation, 5,1 MPs are somewhat flexible on what is installed. A friend has a dual-socket system with 15 GB installed. 3x4 plus 3x1. Before I met him I would have bet more than a beer this wouldn't work. A mutual friend recently upgraded to 32 GB, and gave him his 3x4GB. So hope is on the horizon.
 
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h9826790

macrumors G5
Apr 3, 2014
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Hong Kong
Optimal *memory* speed comes from 3 sticks per CPU, installed correctly. IIRC, there is a 5-7% performance penalty (memory, not overall throughput) for installing 4 sticks per CPU. The presumption here is that the user installs exactly the amount of memory needed (remember, these are server parts). But if the workload requires more memory than is available from the 3 sticks, adding a 4th stick is desirable over hitting swap.
In my observation, 5,1 MPs are somewhat flexible on what is installed. A friend has a dual-socket system with 15 GB installed. 3x4 plus 3x1. Before I met him I would have bet more than a beer this wouldn't work. A mutual friend recently upgraded to 32 GB, and gave him his 3x4GB. So hope is on the horizon.
The Mac Pro is very flexible on RAM indeed.

https://forums.macrumors.com/threads/can-i-mix-memory-size.1903411/#post-21638766
 

orph

macrumors 68000
Dec 12, 2005
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UK
the potential gains from 3 channel are lost by most real life use and if you ever go over your installed ram then the slowdowns are massive, stick it all in.
 

fendersrule

macrumors 6502
Oct 9, 2008
418
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"If" you ever, I guess. For me, 24GB of Ram whilst leaving a slot open is optimal since I've yet to come close to using it all.
 

orph

macrumors 68000
Dec 12, 2005
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@fendersrule use case is important, whwang is talking about 80GB of RAM so he must be using some of the few apps that actually eat ram which means more is better.

use case is relay important, i have 32GB of ram and at times i can go past that with video work on more complex projects but if i ever look at AE then my ram just fills in no time.

id gess as use case is not given it's valid to point out but for some workloads it is needed to have large amounts of ram
 

whwang

macrumors regular
Original poster
Dec 18, 2009
130
69
Yes, I once hit a point that even my old 96GB RAM was not enough. Then I decided to re-write my program and split the job. It's less ideal, but at least it did not take forever to complete the jobs. Swapping the HD and even the SSD is much slower.

That does not happen often, though. Hopefully I won't need to face it again until my 128GB iMac Pro arrives. In the mean time, I think I can accept either 80GB (3*16 + 2*16) or 64GB (2*16 + 2*16). It seems that the 64GB case will give a small speed advantage, based on what people said here, as long as the RAM usage does not exceed 64GB.
 

h9826790

macrumors G5
Apr 3, 2014
14,146
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Hong Kong
Yes, I once hit a point that even my old 96GB RAM was not enough. Then I decided to re-write my program and split the job. It's less ideal, but at least it did not take forever to complete the jobs. Swapping the HD and even the SSD is much slower.

That does not happen often, though. Hopefully I won't need to face it again until my 128GB iMac Pro arrives. In the mean time, I think I can accept either 80GB (3*16 + 2*16) or 64GB (2*16 + 2*16). It seems that the 64GB case will give a small speed advantage, based on what people said here, as long as the RAM usage does not exceed 64GB.
Just try both config in Geekbench, check the memory score, then you will know if only run 4x16 is faster than 5x16. If there is a slow down, the score difference should be very significant (way outside normal error margin). e.g.

3x16GB is like this
3x16.jpg

and 4x8GB is like this
4x8.jpg

As you can see. The multi-core memory performance will be 50% faster if only use 3 slots but not 4. Of course, the real world performance difference will be much much smaller than this because we are not always memory bandwidth limiting, also the system should use cache normally. However, it’s a good indicator if you want to know which RAM configuration is “faster”.
 
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whwang

macrumors regular
Original poster
Dec 18, 2009
130
69
Let me report what I got. I ran Geekbench 4.2 64bit. Here are the key scores.

---------------------------------------------------
64 GB (16GB * 2 + 16GB * 2)

Single-core score: 2641
Crypto Score 1721
Integer Score 3145
Floating Point Score 2357
Memory Score 2164
Memory Copy 1870 5.18 GB/sec
Memory Latency 4398 98.4 ns
Memory Bandwidth 1233 6.59 GB/sec

Multi-core score: 21599
Crypto Score 13889
Integer Score 28412
Floating Point Score 24313
Memory Score 4123
Memory Copy 4864 13.5 GB/sec
Memory Latency 4413 98.1 ns
Memory Bandwidth 3267 17.4 GB/sec
---------------------------------------------------
80 GB (16GB * 3 + 16GB * 2)

Single-core score: 2652
Crypto Score 16u4
Integer Score 3173
Floating Point Score 2358
Memory Score 2163
Memory Copy 1711 4.74 GB/sec
Memory Latency 5816 74.4 ns
Memory Bandwidth 1018 5.44 GB/sec

Multi-core score: 14244
Crypto Score 3616
Integer Score 18151
Floating Point Score 18318
Memory Score 1997
Memory Copy 1630 4.52 GB/sec
Memory Latency 3500 123.7 ns
Memory Bandwidth 1397 7.46 GB/sec
---------------------------------------------------

You can see that the 80GB configuration gets substantial punishment in memory categories, especially the multi-core ones. I think I will stay with 64GB, wait for my iMacPro to arrive, and have OWC replace all the six 16GB modules.
 

monoton

macrumors member
Aug 15, 2006
44
44
Oslo / Tokyo
Let me report what I got. I ran Geekbench 4.2 64bit. Here are the key scores.

---------------------------------------------------
64 GB (16GB * 2 + 16GB * 2)

Single-core score: 2641
Crypto Score 1721
Integer Score 3145
Floating Point Score 2357
Memory Score 2164
Memory Copy 1870 5.18 GB/sec
Memory Latency 4398 98.4 ns
Memory Bandwidth 1233 6.59 GB/sec

Multi-core score: 21599
Crypto Score 13889
Integer Score 28412
Floating Point Score 24313
Memory Score 4123
Memory Copy 4864 13.5 GB/sec
Memory Latency 4413 98.1 ns
Memory Bandwidth 3267 17.4 GB/sec
---------------------------------------------------
80 GB (16GB * 3 + 16GB * 2)

Single-core score: 2652
Crypto Score 16u4
Integer Score 3173
Floating Point Score 2358
Memory Score 2163
Memory Copy 1711 4.74 GB/sec
Memory Latency 5816 74.4 ns
Memory Bandwidth 1018 5.44 GB/sec

Multi-core score: 14244
Crypto Score 3616
Integer Score 18151
Floating Point Score 18318
Memory Score 1997
Memory Copy 1630 4.52 GB/sec
Memory Latency 3500 123.7 ns
Memory Bandwidth 1397 7.46 GB/sec
---------------------------------------------------

You can see that the 80GB configuration gets substantial punishment in memory categories, especially the multi-core ones. I think I will stay with 64GB, wait for my iMacPro to arrive, and have OWC replace all the six 16GB modules.
How did this turn out, did you get the replacement?
 
Last edited:

Superlead

macrumors member
Apr 27, 2020
35
1
Sorry to revive this topic but my question is about the same subject , so i thought i could use this topic instead of opening a new one ( and i will stick to that subject in my post ) .
I would like to update my Ram in my 2010 Mac pro 5,1 2x 2,4 ( 2x quad core ) and Mac pro 4,1 2x 2,66 ( 2x quad core) .
For the moment i have 4 x 2gb in my 4,1 and 6x 4gb in my 5,1 .

I see OWC in UK had some Ram kits with 3x16gb ( whereas i only saw 4GB modules in the shop in Paris i used to buy Apple hardware ) , so i am thinking about buying two kits from OWC .
From what i read above , i can't mix 16gb modules with my 4gb modules if they are not both RDIMM ( as this topic says OWC sell 16GB RDIMM ) and i have no idea if the RAM in my macs is R or UDIMM.

My question is about 32 and 64 bit mode , as it seems both the 8 core 4,1 and 5,1 can support 48GB of Ram in 32 bit mode and 64 to 96 GB in 64 bit mode , using Mac OSX Snow Leopard 10.6 and above .

Say i put 64 GB (4x16) or even 96 GB (6x16) in one Mac , will it work perfectly in 32 bit mode but only using 48GB ( and obviously use the 64 or 96 GB in 64 bit mode ,depending how much Ram i put in it ) or could it be a problem in 32 bit mode if i put more than 48GB of Ram in the Mac using some 16GB modules ?
 
Last edited:

tsialex

macrumors 604
Jun 13, 2016
7,661
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Brazil
Sorry to revive this topic but my question is about the same subject , so i thought i could use this topic instead of opening a new one ( and i will stick to that subject in my post ) .
I would like to update my Ram in my 2010 Mac pro 5,1 2x 2,4 ( 2x quad core ) and Mac pro 4,1 2x 2,66 ( 2x quad core) .
For the moment i have 4 x 2gb in my 4,1 and 6x 4gb in my 5,1 .

I see OWC in UK had some Ram kits with 3x16gb ( whereas i only saw 4GB modules in the shop in Paris i used to buy Apple hardware ) , so i am thinking about buying two kits from OWC .
From what i read above , i can't mix 16gb modules with my 4gb modules if they are not both RDIMM ( as this topic says OWC sell 16GB RDIMM ) and i have no idea if the RAM in my macs is R or UDIMM.

My question is about 32 and 64 bit mode , as it seems both the 8 core 4,1 and 5,1 can support 48GB of Ram in 32 bit mode and 64 to 96 GB in 64 bit mode , using Mac OSX Snow Leopard 10.6 and above .

Say i put 64 GB (4x16) or even 96 GB (6x16) in one Mac , will it work perfectly in 32 bit mode but only using 48GB ( and obviously use the 64 or 96 GB in 64 bit mode ,depending how much Ram i put in it ) or could it be a problem in 32 bit mode if i put more than 48GB of Ram in the Mac using some 16GB modules ?
From MP3,1, all Mac Pros are EFI64 Macs.

MP5,1 hardware is configured to run 64bit kernel from the moment the firmware is loaded. The default mode is 64bit with a MP5,1 running macOS, this is not even a question after 10.7, Snow Leopard will always boot with the 64Bit kernel with a MP5,1.

Since MP5,1 don't support macOS releases older than Snow Leopard, this is again a moot question and later macOS versions than Snow Leopard don't even have a 32Bit kernel.

The only way to force a MP5,1 to run in the 32Bit mode is running CSM 32bit Windows and not using BootCamp, an unsupported configuration.

A MP4,1 still with the original MP4,1 firmware can run Snow Leopard with the 32bit kernel, but no one in the right mind want's that.
 

Superlead

macrumors member
Apr 27, 2020
35
1
From MP3,1, all Mac Pros are EFI64 Macs.

MP5,1 hardware is configured to run 64bit kernel from the moment the firmware is loaded. The default mode is 64bit with a MP5,1 running macOS, this is not even a question after 10.7, Snow Leopard will always boot with the 64Bit kernel with a MP5,1.

Since MP5,1 don't support macOS releases older than Snow Leopard, this is again a moot question and later macOS versions than Snow Leopard don't even have a 32Bit kernel.

The only way to force a MP5,1 to run in the 32Bit mode is running CSM 32bit Windows and not using BootCamp, an unsupported configuration.

A MP4,1 still with the original MP4,1 firmware can run Snow Leopard with the 32bit kernel, but no one in the right mind want's that.

OK , thanks for your answer and sorry i have mixed up two things between 2009 mac pro 4,1 which seems to be able to work in 32 and 64 bit mode from what Everymac website says and Mac Pro 5,1 and also between OSX and Logic Pro 9 that is able to startup with 32 bit or 64 bit ( as i did not upgrade to Logic X yet ).
But as i did not start Logic 9 changing its resolution between 32 to 64 bit for a long time , i mixed up OSX and Logic .
That said as i also read about 32 bit or 64 bit mode and ram capability when reading what was specified about it on EveryMac website about Mac Pro 2009 4,1 ,so i thought Mac pro 2010 -2012 5,1 could also choose between 32 and 64 bit mode and that it had consequences on its Ram capability as for 2009 4,1 it says :

RAM Type, Actual Maximum Capacity, & Performance Details

"Officially, starting December 4, 2009, Apple supports 16 GB of RAM in the "Quad Core" models and 32 GB of RAM in the "Eight Core" models using 4 GB memory modules.
However, site sponsor OWC first discovered that the "Quad Core" models actually were able to support 32 GB of RAM (in both 32-bit and 64-bit mode) and later increased this maximum to 48 GB of RAM.

Likewise, OWC first discovered the "Eight Core" models could support 64 GB of RAM when booting the system in 64-bit mode running Mac OS X 10.5 "Leopard" and later increased this maximum to 96 GB of RAM running Mac OS X 10.6 "Snow Leopard" or later versions of OS X. More recently, OWC yet again discovered these "Eight Core" models can support up to 128 GB, but only when running a 64-bit version of Windows XP or later or Linux. Mac OS X only can support 96 GB of RAM."

And also it seems 32 bit mode was the default boot mode for 2009 Mac Pro 4,1 with Snow Leopard ( whereas it is 64 bit for 2010 5,1 in Snow Leopard ) , so i wonder if mine is in 32 or 64 bit but i will check ( but as it must still have its original firmware i suppose it is 32 bit from what you say as i was still using Snow Leopard on it . Its BootRom is MP41.0081.B08) and if its default boot mode will be 64 bit if i upgrade it to 5,1 ( i suppose yes ) :
 
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KeesMacPro

macrumors 6502
Nov 7, 2019
254
56
@Superlead
Logic Pro 9 ,if I'm not mistaken, ran even on G5 machines, thats a long time ago....

I would stick to a "rule of thumb" like:
hardware and software about the same age.
"old" hardware + "new" software = no good
"new" hardware + " old" software = no good
"old" hardware + "old" software = good
"new" hardware + "new" software = good

Honestly, if I may say so, I would go step by step.
There's so much info on the internet and lots is close to nonsense..
this can confuse a lot...

On this forum there's lots of valuable information that could help you , because , naturally, lots of people want the same thing, running into the same doubts, issues etc etc
Take your time to digest all the info people on this forum gave to you.
Based on the BootRom thread for example, you could make a checklist of the things to have to do and/or check.
and when you think you're ready, go for it .
Doucement.
 

Superlead

macrumors member
Apr 27, 2020
35
1
@Superlead
Logic Pro 9 ,if I'm not mistaken, ran even on G5 machines, thats a long time ago....

I would stick to a "rule of thumb" like:
hardware and software about the same age.
"old" hardware + "new" software = no good
"new" hardware + " old" software = no good
"old" hardware + "old" software = good
"new" hardware + "new" software = good

Honestly, if I may say so, I would go step by step.
There's so much info on the internet and lots is close to nonsense..
this can confuse a lot...

On this forum there's lots of valuable information that could help you , because , naturally, lots of people want the same thing, running into the same doubts, issues etc etc
Take your time to digest all the info people on this forum gave to you.
Based on the BootRom thread for example, you could make a checklist of the things to have to do and/or check.
and when you think you're ready, go for it .
Doucement.
Yes , i understood there are skilled people here , like tsialex for example but others as well ,that is why i ask some questions here but yes, it is much infos going back ten years ago and undrstanding things since .

That said, yes ,it is best to use recent equipment or older ones together but as i explained in my other threads i cannot upgrade my whole system now ( too expensive to spend tens thousands of dollars) and my pro tools HDX hardware ( + softwares) system ( that i also use with Logic pro software ) is still sold new and my mac pros both still work with recent softwares and OSX except catalina ( although pro yools HDX system still works in the 2019 /2020 mac pro and Catalina whereas it was released in 2011 , even if they released a new MTRX 384khz audio converter), so even if " old" , they are still up to date if i can say it like that and very high end professional equipment ( see my other thread for more infos ).
 

KeesMacPro

macrumors 6502
Nov 7, 2019
254
56
Last edited:
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