Question Memory upgrade for dual CPU HP Z620


May 30, 2014
I have a dual-cpu HP Z620 and I want to upgrade the memory, but I'm confused about some things on HP's : - specifically page 2.

I have four 8GB DIMMS to put in the four slots of CPU 1. That is clear. One thing is that the 48GB row is the same as the 64GB row, but that must be an error.

I want to get to a total of at least 64GB (I've ordered four 8GB DIMMS for that), but right now I don't want to spend the money for eight 8GB sticks, to get to 96GB. But I have four extra 4GB sticks. Since I needed either four more 4GB sticks (for the top line of 64GB) or four more 8GB sticks (for the second line of 64GB); I've ordered 4x8GB. But according to this, if I mix 4GB and 8GB sticks on CPU0 it will hurt the performance. Is that true? I'd rather have 64GB of the best performance than 80GB of not-as-good performance.

A second thing that is confusing me is the table for a single CPU. The 48GB line there shows that mixing 4GB and 8GB sticks will achieve top performance. But that seems to contradict the 80GB line for two CPUs.

So, the bottom line is that I'm putting in four 8GB sticks for CPU1. I will have four 8GB and four 4GB sticks available for CPU0. Should I use just the 8GB sticks for CPU0 or will the performance actually be hurt if I mix 4GB and 8GB sticks on CPU0?


I'd take the chart you've provided and stick to it as best as possible. Since the board makers themselves are HP, you should adhere to their guideline for best performance. That is, loading out all channels with 8GB sticks of ram, that are exactly identical.