Is Command Rate IMC or DIMM bound?

[Vasllo]

I built an E5 2640 V3 with 3x8GB Netac DDR4 1600MHz (actual clock) in triple-channel on a Huananzhi X99-TF (best chinese X99 v3 option), and I often see people running this CPU with memory at CR 1T, but my CR is at 3T and there's no way to change it other than, maybe, a BIOS mod, which would brick it if a lower CR isn't stable. Now, is this because of a terrible IMC, or bad memory? Just in case, I'll post the CPU-Z of the CPU and memory.

 

I noticed this when watching a review of the E5 2666 V3, because my memory bandwidth is WAY lower than what it should be, and the worst offender in the memory timings is the Command Rate.

 

I'm considering going for an E5 2666 V3 for the couple more cores (since they aren't particularly fast ones), 100MHz higher clock and higher memory clock (933MHz vs 1066.5MHz, DDR3 speeds on DDR4, lol), and possibly solving the bad IMC issue, if it actually is the IMC's fault.

 

Also, I didn't check what it was before modding the BIOS to unlock single thread clock boost for all cores, but I did undervolt both the CPU and IMC with -50mV. I just realised this might've caused this as I posted this, so I'll try and flash the BIOS without IMC undervolt in a couple days, because I can't do it rn.

 

 

[Guest]

Just before I would give any insite on this one, we need to see the SPD tab of the memory. It will request the board to run 3T if that's how the memory is designed. 

[Vasllo]

1 hour ago, Guest 5150 said:

Just before I would give any insite on this one, we need to see the SPD tab of the memory. It will request the board to run 3T if that's how the memory is designed. 

 

Well, seems like the issue might be exactly the memory's profile. I tried retraining and removing some DIMMs, but it went back to 3T.

 

[Vasllo]

Actually, I just thought about a bit more, and googled this SPD page of CPU-Z and none of the images I saw had the Command Rate value, which leads me to think it's actually a timming controled only by the IMC, and the memory doesn't care about it, as it's not in the profile table. Looked for some more definitions of CR, and it does seem to align with this. I'll try to reset back the IMC voltage and see if it holds 2T, at least, if not, I'll probably try and get the E5 2666 V3 in a bit and hope it makes a difference, lol.