Resolved 2010 Mac Pro Memory Speed Mismatch?

[m1maverick]

I have a 2010 Mac Pro 2 x 3.46GH 6-core processors which had 4 x 8GB (32GB total) 1066MHz memory. I decided to bump it up to 64GB and purchased 4 x 8GB (32GB total) 1333Mhz memory. When I installed the new memory the system does not boot and has a flashing power light (I didn't observe the flash pattern). To troubleshoot I began swapping memory around in. In the end the system boots with either set (1066MHz or 1333MHz) in either bank 1 (slots 1, 2, 3, and 4) or bank 2 (slots 5, 6, 7, and 8). It just doesn't work when both sets of memory are installed. I read Apple's documentation on upgrading at it appears all I need to do is ensure the same speed memory is used in the same bank so memory placement doesn't appear to be the issue.

It is my understanding the 1066MHz and 1333MHz memory should be useable with the system clocking down to the speed of the slower memory. Is my understanding incorrect?

 

[Nguyen Duc Hieu]

I have a 2010 Mac Pro 2 x 3.46GH 6-core processors which had 4 x 8GB (32GB total) 1066MHz memory. I decided to bump it up to 64GB and purchased 4 x 8GB (32GB total) 1333Mhz memory. When I installed the new memory the system does not boot and has a flashing power light (I didn't observe the flash pattern). To troubleshoot I began swapping memory around in. In the end the system boots with either set (1066MHz or 1333MHz) in either bank 1 (slots 1, 2, 3, and 4) or bank 2 (slots 5, 6, 7, and 8). It just doesn't work when both sets of memory are installed. I read Apple's documentation on upgrading at it appears all I need to do is ensure the same speed memory is used in the same bank so memory placement doesn't appear to be the issue.

It is my understanding the 1066MHz and 1333MHz memory should be useable with the system clocking down to the speed of the slower memory. Is my understanding incorrect?

Maybe there are more difference than just speed.
RAM type, perhaps? Non-ECC vs ECC RAM, Registered RAM?

 

[tsialex]

Probably you bought RDIMM and the old modules are UDIMM. You can't mix and match memory types, you can only use one type of memory.

Upload photos of both so we can confirm it.

 

[m1maverick]

Probably you bought RDIMM and the old modules are UDIMM. You can't mix and match memory types, you can only use one type of memory.

Upload photos of both so we can confirm it.

That sounds reasonable. Here are pictures, top is the original memory and bottom is the new memory. Can I assume the "R" after the 10600 stands for RDIMM and the lack of an "R" after the 8500 indicates UDIMM?

 

[Nguyen Duc Hieu]

That sounds reasonable. Here are pictures, top is the original memory and bottom is the new memory. Can I assume the "R" after the 10600 stands for RDIMM and the lack of an "R" after the 8500 indicates UDIMM?

Lack of the R doesn't always indicate UDIMM, but it's surely not an RDIMM.

 

[tsialex]

That sounds reasonable. Here are pictures, top is the original memory and bottom is the new memory. Can I assume the "R" after the 10600 stands for RDIMM and the lack of an "R" after the 8500 indicates UDIMM?

View attachment 1912488

View attachment 1912489

Since the label of the first one don't show any more info, upload a picture of the full DIMM, then we can see if it's UDIMM or not. RDIMMs also have a register controller CI.

 

[m1maverick]

Since the label of the first one don't show any more info, upload a picture of the full DIMM, then we can see if it's UDIMM or not. RDIMMs also have a register controller CI.

I think I am going to order another set of 1333MHz memory. Each set of DIMMs works individually and they both work in either bank. This suggests the two sets of memory are incompatible with one another. I was on the fence if I should buy another set of 1333MHz but figured the performance gains, for what I do, were almost nil. Now I have a reason to buy them. I'll report back once I receive the second set.

 

[m1maverick]

I wanted to update this thread with the resolution. I ordered a second set of memory from the same seller and all is now good. There definitely was an issue between the original and the new memory which has been resolved with 8 sticks of the same memory.