Mac Pro 5,1 - RAM Compatibility - Mixed

Vilhelm.83

macrumors newbie
Original poster
Jun 30, 2017
2
0
Ottawa, Ontario
I've got a 5,1 Mac Pro (2009 Firmware upgrade) which I've recently upgraded to a new CPU tray with 2 x 3.46 GHz 6-Core Intel Xeon. I've been successfully running 32GB (4x8GB) 1333 memory in it since I updated the firmware a few years ago. The memory has carried over on the upgrade and has continued to work fine. Now that I have 4 more slots, I thought it would be a good opportunity to ad another 32GB. I ordered another set of 4x8GB. After installing the the new DIMM's the Mac won't boot , and I get the blinking front light. I've removed the older DIMM's to test the machine with the just the 4 new DIMM's and it boots no problem. Tried removing one of the new DIMM's and replacing it with one of the older ones, and it doesn't boot.

So, the Mac boots with the old RAM. The Mac boots with the new RAM. The Mac doesn't boot with a mix of the RAM.

These are the original sticks I was using.

Apple® — 974044A - 32GB (4x8GB) DDR3 ECC UDIMM PC3-10600 9-9-9-24 Apple ECC (974044A)

And these are the new ones I just ordered.

32GB (4X8GB) MEMORY PC3-10600 1333MHZ 1.5V ECC REG DDR3 240 PIN DIMM 2RX4

The ones I just received seem to differ from the add. I actually received Kingston 8GB 2Rx4 PC3L - 10600R - 9-12-E2. Which appear to be a lower voltage (PC3L?) if I'm not mistaken. I'm not overly versed in memory so I'm not too sure if I should request a replacement or not. The add mentioned I may receive different manufactured sticks, but they would all meet the same specs. And Like I said, the machine boots with it, and does show ECC Enabled in the system profiler.

Just wondering if I'm crazy, but these sticks should be compatible with each other, no? Is there anything else I can check, or test to see if I'm on the right path? Or could there be other issues I've created since upgrading my tray and CPU's?


 

ActionableMango

macrumors G3
Sep 21, 2010
9,263
6,251
Just wondering if I'm crazy, but these sticks should be compatible with each other, no?
No, the Apple ram is unbuffered and the Kingston RAM is registered. These two types of RAM can work independently but cannot be mixed in the same computer.

I would return the Kingston RAM. 10600R ("R" for registered) is NOT the same spec as the advertised 10600. An exchange for equivalent unbuffered modules would be acceptable.
 
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Vilhelm.83

macrumors newbie
Original poster
Jun 30, 2017
2
0
Ottawa, Ontario
Thanks. Looking through the ad's item specifics, it does mention registered. So it looks like I may be out of luck for a return. May have to do another order and eat the cost on that last batch.

Forgive my ignorance, but as it stands now I can either order another set of Registered or Unbuffered to fill my machine. Is one preferred over the other? Doing a quick search on the subject was mostly out of my comprehension. This machine is primarily used for After Effects, Premiere, and Cinema 4D if that makes any difference.
 

h9826790

macrumors G5
Apr 3, 2014
12,782
5,592
Hong Kong
Correct, you need to order another 4x8GB or RAM to make it 64GB in total.

There is almost no restriction on mixing RAM in cMP as long as the spec is correct, EXCEPT, UDIMM cannot be mixed with RDIMM.

You can mix ECC with no ECC. Mixing 1GB, 2GB, 4GB, 8GB, DIMMs all together. Mix 1066 with 1333, etc. But you cannot boot from UDIMM mix with RDIMM.
 
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ActionableMango

macrumors G3
Sep 21, 2010
9,263
6,251
So it looks like I may be out of luck for a return. May have to do another order and eat the cost on that last batch.

Forgive my ignorance, but as it stands now I can either order another set of Registered or Unbuffered to fill my machine. Is one preferred over the other?
The ad states 30 day return policy. I would return it, eat the restocking fee instead of the whole amount, and buy unbuffered RAM to match your existing RAM.
 
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Chris Johnson

macrumors newbie
May 10, 2018
2
0
Oakland California
I just attempted to upgrade my Mac Pro 5,1 by simply adding OWC 8 gb ram to the set of 2 gb ram that I had installed and discovered that this combination did not work. What solved my blinking power light problem was simply removing the old ram and running only the new, and faster owc ram.
 

h9826790

macrumors G5
Apr 3, 2014
12,782
5,592
Hong Kong
I just attempted to upgrade my Mac Pro 5,1 by simply adding OWC 8 gb ram to the set of 2 gb ram that I had installed and discovered that this combination did not work. What solved my blinking power light problem was simply removing the old ram and running only the new, and faster owc ram.
OWC is one of the worst company about selling RAM. They don’t even tell you the DIMM spec which is very important for every single computer.

Most likely your 8GB sticks are RDIMM, and the 2GB one are UDIMM. Therefore, can’t work together.
 
Last edited:

Chris Johnson

macrumors newbie
May 10, 2018
2
0
Oakland California
Most likely your 8GB sticks are RDIMM, and the 2GB one are UDIMM. Therefore, can’t work together.[/QUOTE]

I'm not sure how I'd find those specs but I'm very happy with the outcome.

Thanks
 

Surrat

macrumors 6502
Jun 20, 2014
478
154
United States
If you look up what registered memory is for, it is actually faster than unregistered when using more than one stick.

I have switched all my late model mac pros to registered ecc ram.
Specifically, this kind: https://www.ebay.com/itm/Hynix-8GB-2Rx4-PC3-10600R-Server-Memory-LOT-OF-4/273134855735

Keep in mind also that 3 sticks per cpu of matching ram gives max speed, and 4 sticks is actually slightly slower than 2 sticks due to memory controller behavior. If you need the memory, sure, use 4 sticks per, but if 3 will give you enough, use 3.

I'm not affiliated with the memory seller, its just an example of the rdimm model I use.