Anu0512 wrote:jleonard711
Your RAM are working fine ? can post some details like brand. I have one question right now I have 16 GB in four solt and other four solt are empty so if i put other brand RAM same like you so they will work with this RAM
Yes, my RAM is working fine. I have two Z420 systems (one has 32GB and the other has 16GB), and both are using ECC Registered (RDIMM) memory. Even though the HP whitesheet says to use unregistered/unbuffered memory, the registered memory works just fine and is actually cheaper because it's more common and easier to find. The 16GB that I bought most recently are Samsung 4x4GB modules with the HP P/N 500203-061, and I paid $20 delivered for 16GB!
And yes, if you have 4 slots populated with 16GB (4x4GB) then you can add 4 more for a total of 32GB. And they can be different brands, but you'll want to make sure they are the EXACT same speed, capacity, and rank (i.e. 2Rx4, 2Rx8, etc). While this will increase your total RAM capacity, keep in mind that it will actually decrease your RAM performance. The reason for this is that the CPU & motherboard support 4 channels, so having 8 slots on the motherboard means each channel has 2 slots. But the bandwidth of 2 slots is limited to what a single channel can handle, so putting 2 sticks into the same channel (1 black, 1 white) will double the capacity but those sticks will need to share the bandwidth of a single channel rather than each having their own dedicated channel. If you want the best performance with 32GB you remove the 4x4GB sticks that you have now and get 4x8GB sticks instead.