Which memory is faster?

[zombie67]

I have an old dual v2 xeon. I bought it as a referb, and came with 8x8gb. I happened to have four 16gb DIMMs that I think are compatible. So I swapped those out with 4x16gb, hoping it would be faster. But I am not really sure how fast this old machine can run memory, regardless of the speed of the DIMMs. Here is what CPU-Z tells me. Is it possible to tell by this info, which is faster? I am having trouble telling because one has a higher frequency, but the other has lower latency. Of course, I could be reading this all wrong.

8x8gb:
https://www.dropbox.com/s/qd4x140kvtlrdnp/8x8.jpg?raw=1

4x16gb:
https://www.dropbox.com/s/egie9dkrgzn45mv/4x16.jpg?raw=1

[John P. Myers]

The 8x8 will be much faster because that allowed each Xeon to have 4 modules. When you switched to 4x16, each Xeon only had 2 modules which cut bandwidth in half.

[zombie67]

Well dang. I thought I was starting to understand memory, but I guess not. I thought that 4xN is faster than 8x(N*.5)?

[John P. Myers]

Well dang. I thought I was starting to understand memory, but I guess not. I thought that 4xN is faster than 8x(N*.5)?4x is faster per cpu than 8x. But it's per cpu.

For mainstream cpus, 2x is faster.

[zombie67]

Ah. Per CPU. I thought 4 channels meant 4 DIMMs. But the rule is "one DIMM channel, per CPU"? So in this case, the CPU has 4 channels x 2 CPUs = 8 DIMMs?

Any chance I could have known your answer from the numbers in the images I posted? What would have told me what you summarized? Or was the info from CPU-Z not sufficient to make a decision?

[John P. Myers]

Ah. Per CPU. I thought 4 channels meant 4 DIMMs. But the rule is "one DIMM channel, per CPU"? So in this case, the CPU has 4 channels x 2 CPUs = 8 DIMMs?

Any chance I could have known your answer from the numbers in the images I posted? What would have told me what you summarized? Or was the info from CPU-Z not sufficient to make a decision?Yes, 4 channels x 2 CPUs = 8 DIMMs is the right way to look at it.

CPU-Z shows in the upper righthand corner the "Channel #". With 8x8 it says quad and with 4x16 it says dual.