MP 1,1-5,1 1333 MHz or 1066 MHz ?!?!

frilli

macrumors newbie
Original poster
Jul 2, 2019
15
1
Good morning, sorry for my bad english,

I have a Mac Pro 5.1 Dual Core Intel Xeon x5675 da 3,06 GHz.....

....because if install 6 memory banks of 8 gb (total 48GB) it works at 1333 MHz, instead if I install all 8 banks (total 64 GB) it works at 1066 MHz ???

I can not understand !!!

The memory is Kingstone ... I changed two different models, nothing to do !!!! Why ???

Thanks !!
 

h9826790

macrumors G5
Apr 3, 2014
12,800
5,622
Hong Kong
Good morning, sorry for my bad english,

I have a Mac Pro 5.1 Dual Core Intel Xeon x5675 da 3,06 GHz.....

....because if install 6 memory banks of 8 gb (total 48GB) it works at 1333 MHz, instead if I install all 8 banks (total 64 GB) it works at 1066 MHz ???

I can not understand !!!

The memory is Kingstone ... I changed two different models, nothing to do !!!! Why ???

Thanks !!
Because wrong memory rank.

You should use 2Rx4 memory (dual rank). Quad rank memory (e.g. 4Rx4) will force the memory to run at lower clock when share use the same channel in slot 3 and 4 (also slot 7 and 8).
 
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kazkus

macrumors member
May 25, 2019
44
50
San Francisco, CA, USA
if install 6 memory banks of 8 gb (total 48GB) it works at 1333 MHz, instead if I install all 8 banks (total 64 GB) it works at 1066 MHz
I experienced the same (or similar) phenomenon.
My configuration was:
* MacPro5,1 with Boot ROM 144.0.0.0.0
* macOS Mojave 10.14.5
* dual X5680
* memory: Micron MT36JSZF1G72PZ-1G4D1DD 8GB 2Rx4 1333MHz ECC
Recently in May 2019, I confirmed that 64GB (8x 8GB) ran at 1066MHz.
( I have not checked 48GB (6x 8GB) with this configuration yet. ) .. (*1)

However, I checked the old log, and found that 8x8GB actually ran at 1333MHz on OS X Yosemite 10.10.5.
At that time, its Boot ROM was MP51.007F.B03, so I doubt of the recent Boot ROM which comes with Mojave or High Sierra, but I am not so sure.
( I have not tried 8x8GB memory with OS X Yosemite 10.10.5 and BootROM 144.0.0.0.0 yet. ) .. (*2)

Currently, I don't have much time to test the above configurations (*1) and (*2).
 
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MIKX

macrumors 65816
Dec 16, 2004
1,213
453
Japan
The ( my ) Early 2009 Dual Quad "2.93Ghz" 4.1 cMP "apparently" - is unique in that it accepts 1333 Mhz natively even without the " 4.1 > 5,1" flash update .. . but I have never tested this. . can anyone confirm this ?
 

frilli

macrumors newbie
Original poster
Jul 2, 2019
15
1
Because wrong memory rank.

You should use 2Rx4 memory (dual rank). Quad rank memory (e.g. 4Rx4) will force the memory to run at lower clock when share use the same channel in slot 3 and 4 (also slot 7 and 8).
The memory is this .... I also tried its 1333 MHz variant .... same problem !!!
 

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frilli

macrumors newbie
Original poster
Jul 2, 2019
15
1
As I said before, you should use 2Rx4 DIMM. The manual you attached shows that’s a 2Rx8 DIMM.
Ok I understand ... in your opinion
.... better 48 GB at 1333 MHz, or 64 GB at 1066 MHz ???
 

Flocarino

macrumors regular
Jun 4, 2010
148
18
Montreal, Canada
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kazkus

macrumors member
May 25, 2019
44
50
San Francisco, CA, USA
What CPU do you have? Exact model, not just speed.
According to his signature, it seems that they are dual X5690.

I got this 96GB kit today and once installed it shows 96GB 1066MHz...reset the PRAM and no change. Is it normal? It clearly says 1333 MHz on them? Is it related to the 2R4 RANK and 4R4 RANK and if yes, why show 1066 MHz since it is in an original 5.1?
Also, what is your Boot ROM version and macOS version ?
Before replacing memory, did your 48GB (6x 8GB) memory run at 1333MHz ?

It might be because your new 16GB memory modules are 4Rx4, but it might be another reason.
I have a similar issue that it runs at 1066MHz in some configurations, and plan some testing later this week.
 

Flocarino

macrumors regular
Jun 4, 2010
148
18
Montreal, Canada
Boot ROM 144.0.0.0
OS Mojave the latest. 10.14.5
The previous 48GB run at 1333MHz it says 2Rx4 on them comparing to the 4Rx4 on the 16GB ones, but it doesn’t make sense.
1333MHz should run at 1333MHZ and not backwards.....unless the stickers on the RAM chips are counterfeit and the sticks are actually 8500 in fact.:mad:
 
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h9826790

macrumors G5
Apr 3, 2014
12,800
5,622
Hong Kong
1333MHz should run at 1333MHZ and not backwards
Memory rank can affect the highest clock speed that can run on the cMP. A user should get the correct spec hardware, not the DIMM's fault.

If your logic is correct, than a 1600MHz DIMM should run at 1600MHz on cMP but not backward. Does that make sense? The cMP simply not compatible to do that. Same as you install a "wrong" memory rank DIMM onto it.
 

Flocarino

macrumors regular
Jun 4, 2010
148
18
Montreal, Canada
Memory rank can affect the highest clock speed that can run on the cMP. A user should get the correct spec hardware, not the DIMM's fault.

If your logic is correct, than a 1600MHz DIMM should run at 1600MHz on cMP but not backward. Does that make sense? The cMP simply not compatible to do that. Same as you install a "wrong" memory rank DIMM onto it.
Then, the seller should add this in his Ebay ad, saying that the clock doesn’t mean nothing, it is the rank that counts. Simple as that: 16GB 4RX4 may run at an undetermined clock depending on your hardware......


Basically I should have bought these ones since 1600MHz would have run at 1333MHz in a cMP, correct or not?
https://www.ebay.ca/itm/96gb-Kingston-6x-16GB-2RX4-PC3-12800R-DDR3-Reg-ECC-Server-Memory-SL16D316R11D4/293098924983?hash=item443e0eabb7:g:IL8AAOSwB8RbwiTv
 
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amedias

macrumors regular
Feb 9, 2008
186
155
Devon, UK
Then, the seller should add this in his Ebay ad, saying that the clock doesn’t mean nothing, it is the rank that counts. Simple as that: 16GB 4RX4 may run at an undetermined clock depending on your hardware......
No, the Ram can run at its advertised clock in a machine that that supports it and in a supported configuration, it's not the Ram at fault here as there re machines that can run Quad rank dimms at 1333 (and above), but the mac Pro is not one of them. The Mac Pro will run Ram at various speeds and it's dictated by the CPU, slot configuration, and ranks. If you use Quad rank dimms then it will down clock to 1066.

It will also downclock if you use more than a certain number of ranks in any channel, so even using 2x Dual rank in slots 3 and 4 together will make it downclock. The speed isn't 'undetermined' the Nehalem/Westemere memory architectures are well documented as there's even more to it than above which can cause downclocking to 800 as well.

As other posters have said above, stick to the published supported specs and it will work as described.
 
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bsbeamer

macrumors 68020
Sep 19, 2012
2,402
1,116
It is all detailed in my signature
According to his signature, it seems that they are dual X5690.
Just an FYI for future needs, when someone is asking for help it's best to include this type of information in the post itself rather than typing an "it's all in my signature" response. Signatures are not visible to all users and never show up on mobile browsers. It's nearly impossible to figure that information out by guessing...
 
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Flocarino

macrumors regular
Jun 4, 2010
148
18
Montreal, Canada
Just an FYI for future needs, when someone is asking for help it's best to include this type of information in the post itself rather than typing an "it's all in my signature" response. Signatures are not visible to all users and never show up on mobile browsers. It's nearly impossible to figure that information out by guessing...

Something else that I should know....!!!!

From RAM to SIGNATURE....what next?

Let's pull out all the posts where members are asked to put all the required INFO of their hardware in the signature:rolleyes:
[doublepost=1562790378][/doublepost]
As other posters have said above, stick to the published supported specs and it will work as described.
I am, By The Way, way within the official supported specs (REGARDING MEMORY) as you can see below (from Apple)
https://support.apple.com/kb/sp589?locale=en_US
..Don't want to sound sarcastic or anything but when I'll change my Mac, I will make sure to get all the info of the machine down to the name of the employees on the assembly line where my Mac was produced.o_O

My 2 Cents
 
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Macschrauber

macrumors 6502
Dec 27, 2015
492
215
Germany
Your not within the specs (up to 64 gig they say for dual cpus)

You dont want to understand what you dislike.

4rx4 will downclock the memory.
 
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amedias

macrumors regular
Feb 9, 2008
186
155
Devon, UK
I am, By The Way, way within the official supported specs (REGARDING MEMORY) as you can see below (from Apple)
https://support.apple.com/kb/sp589?locale=en_US

My 2 Cents
The full specs are here: https://support.apple.com/en-gb/HT205043#2

Memory card specifications - PC3-10600E, 1333 MHz, DDR3 SDRAM UDIMMs and RDIMMs
- Error-correcting code (ECC)
- 72-bit wide, 240-pin ECC modules
- 36 ICs maximum per ECC UDIMM*

(*although that specifically says UDIMM, I believe the same is true when using Registered DIMMs, there was another article on the Apple site but to seems to have been archived, I'll see if I can dig out a copy.)

^ that means if you're using 4bit wide DRAMs (the x4 bit in the Dimm spec) then you have to use Dual rank to abide by the 36 IC max (18 ICs per rank for ECC).

Quad rank dimms are not officially supported, they will work, but as you've found they will downclock and not run at the full 1333 speed, and you can't use more than 3 dimms of Quad rank per CPU (without downclocking further to 800 or in some cases not booting) as the way the Nehalem/Westmere's and slots are configured in the Mac Pro means they have issues beyond 12 ranks total per CPU.

It gets even more complicated when you work with bigger machines with more ram slots, jsut as a quick example here's the info for an HP server of similar vintage that uses Nehalem and Westmere CPUs, have a look at the table and see the impact of changing ranks and number of DIMMs per channel etc.

https://support.hpe.com/hpsc/doc/public/display?docId=c02215414

Nobody is cheating you, or misleading you, or giving you wrong info. You simply bought memory that is not the required spec to run at the speed you want. Buy the correct spec Ram and it will.

Presumably you posted here asking for advice/an answer? You've been given the answer, if you don't like the answer that's unfortunate but it doesn't stop it being correct.
 
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Flocarino

macrumors regular
Jun 4, 2010
148
18
Montreal, Canada
The full specs are here: https://support.apple.com/en-gb/HT205043#2

Memory card specifications - PC3-10600E, 1333 MHz, DDR3 SDRAM UDIMMs and RDIMMs
- Error-correcting code (ECC)
- 72-bit wide, 240-pin ECC modules
- 36 ICs maximum per ECC UDIMM

^ that means if you're using 4bit wide DRAMs (the x4 bit in the Dimm spec) then you have to use Dual rank to abide by the 36 IC max (18 ICs per rank for ECC).

Quad rank dimms are not officially supported, they will work, but as you've found they will not run at the full 1333 speed, and you can't use more than 3 dimms of Quad rank per CPU as the Nehalem/Westemere's used in the mac Pro top out at addressing 12 ranks per memory controller (ie: per CPU)

Nobody is cheating you, or misleading you, or giving you wrong info. You simply bought memory that is not the required spec to run at the speed you want. Buy the correct spec Ram and it will.

OK, so show me a CORRECT module(link)....because what I linked in post 15 has been ignored.
 

Flocarino

macrumors regular
Jun 4, 2010
148
18
Montreal, Canada

amedias

macrumors regular
Feb 9, 2008
186
155
Devon, UK
OK, so show me a CORRECT module(link)....because what I linked in post 15 has been ignored.
If you find DIMMs listed as 16GB 2Rx4 PC3-10600R then they will work at 1333

EDIT, the ones you linked to in post 15, although they are higher speed DIMMs will downclock to 1333 in a Mac Pro just fine, that's actually the same spec as some of the DIMMs I have in mine (mixed with 10600), but you don't have to buy 12800, Dual rank 10600 will work and should be a little cheaper.
 
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