I don't know much about motherboards and chipsets. These are two Sandy Bridge HP Z420s. The documentation says: PC3-12800E 1600MHz DDR3. Then it says that 1600MHz, 1333MHz, and 1066MHz are supported.
I don't seem to be getting the memory speeds the docs say.
#1:
CPU: Xeon E5-2680
MB: HP 1589
RAM: 8x4GB, 800MHz, 11-11-11-28 (from Speccy)
SSD/HD: ADATA SU635 480GB
GPU: NVidia GeForce 8400GS
PSU: HP
Case: HP
OS: Windows 10 pro 64-bit
#2:
CPU: Xeon E5-2690
MB: HP 1589
RAM: 4x8GB, 666MHz, 9-9-9-24 (from Speccy)
SSD/HD: Seagate ST1000
GPU: NVidia GeForce GT 710
PSU: HP
Case: HP
OS: Windows 10 pro 64-bit
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Several hours later:
Well, I found out that Task Manager/performance/memory also gives the speed of the memory bus. I tried it on four computers, and in all four cases, it showed twice the speed as Speccy shows (1333 vs, 666 and 1600 vs. 800). So maybe Speccy is reporting half of the actual speed.
So back to the original question, is there much of a difference between 800MHz, 11-11-11-28 and 666MHz 9-9-9-24?