how to pick up correct RAM

[BurningSoul1]

in my Z640, theres DDR4 RAM installed in two slots. In total 16 GB, what is way too low. i am going to upgrade. What features must be on board?

- same speed like original one

- registered

- unable to see if buffered or unbuffered in almost all offers I see

I understand the safest way would be to get same modules like installed already, but this will not be the case.

and is it better to install in one slot 16 GB or in two slots 2x8 GB? 

[banhien]

@BurningSoul1 

You can use a tool called CPU-Z to find its existing RAM (brand, model, ... ) then buy the same

          

Regards.

[SDH]

BurningSoul1,

The Z620/Z420 motherboards have a big difference in memory slots when you compare to those in the Z640/Z440 workstations. Specifically, the number of slots in the Z620 is 8 just like it is for the Z420. For the Z640 there actually are only 4 slots but 8 on the Z440. The other 4 pinouts on the Z640 motherboard are bare.

The point is that memory choices for a Z640 are more limited if you're only running one processor. What are you running? If only one then are you planning on adding a riser motherboard plus a second processor?

Also, the Zx40 workstations can only officially run the v3 and v4 processors approved by HP and are you currently running a v3 or a v4? Which one(s)? If so, are you planning on shifting from a v3 to a v4? If so, which one(s)?

This is not a one-size-fits-all issue. Let's start with that...

[BurningSoul1]

ok, there was installed 2540 v4, which i succesfully replaced with 1650 v4. This works stable after some burn tests. I am not planning to add second CPU, as it is not required for my needs. I have 4 slots on mobo, currently 2 outside slots are occupied by 8GB RAM modules (there is picture in the case in which slot which memory). So, this constellation keeps me with two slots free. 

i can buy probably same modules (so additional 2x8GB), but I dont want to, bcs these modules are overpriced even for server modules (Samsung ones). I do not posses any documentation saying what is possible to install and what not. Therefore, from this reason I try to collect informations, what technical features are required to work with this RAM and try my luck with less expensive ones.

the question is also, if is it better to add 2x8GB modules or just 1x16GB and last slot keep empty for future upgrades (if at all). I understand if I add 2x8GB, it will work in quad channell, but then next question, what is the performance difference if it works with 2x8 GB installed already and additional 16 in third slot.  I dont run the z640 as server, neither as digital content creating. Only as pc for gaming (I received it as a gift) and since my old pc was 2 CPU generations older, I switched here ( I can install better graphic card - 1 kW PSU - I can install more RAM, just CPU is end station here, but for current games it has enough speed and cores for FHD gaming)

[SDH]

I searched for what you say was your original single processor and it does not look like Intel made a "E5-2540 v4" processor. They do make a E5-1650 v4 processor that works well in the Z440/Z640 as a single processor.

Try that free utility provided to you in this post and copy/paste in the results. Get the 2 pages that results if you go to the "Memory" and "SPD" tabs you see there at the top.

Also, it sounds like you are planning on keeping your current RAM in place and adding two more sticks into your two empty slots. Correct?

[BurningSoul1]

Yes 1650v4 is now was something weaker there 

yes I plan add 2 (or one) additional kits bcs 16gb is not enough

[BurningSoul1]

And it was e5-2620v4

[SDH]

Your original processor could only run up to 2133MHz so that might be all that you have in place in terms of memory speed. However you need to check what your two current memory sticks are rated for. If 2133 then you'll be stuck at that speed even if you buy 2400 or faster memory for your next two sticks because the 2 faster sticks will automatically slow down to match the two slower sticks. However, HP often installed faster memory rather than trying to match the memory speed to the slower processor's speed. So, you might have true 2400 sticks already in place. In that case I'd go for 2400 or faster memory for your new sticks (they can't run faster than 2400 in any Zx40, regardless).

It turns out in the later Zx40 builds it was actually cheaper for HP to source memory that could run at 2666MHz than to find 2400MHz memory, so searching for recycled 2666 memory might get you better pricing on eBay. I've tested the even-faster memory that HP installs in the Z4 G4 in our Z440/Z640 workstations and it runs just fine. It will down-regulate to running at 2400 max, however, because that is the fastest the Zx40 motherboards can run at.

I've attached the latest Z640 QuickSpecs below, and also a late edition DDR3/4 HP PDF that gives the memory "option" part numbers. Look at the listings for the Z640 at the end of that first PDF document. Most valuable for you will be examples of HP memory in the 8GB or 16GB each stick categories, all specifically for the Zx40 workstations. Remember that all these sticks will be ECC Registered. A few pics are included  below to show proof in the packing labels. Keys to the kingdom:

2400 8GB =T9V39AT & AA =809079-581

8 GB example

2400 16GB =T9V40AT & AA =809082-591

(there are 32 and 64GB sticks too)

I just located some of the HP 16GB later Zx40 official HP sticks for 18.00 each on US eBay... one source had 2400MHz ones and another had 2666, shown below, with same HP part number. This is an example of HP providing the faster memory for no added cost. All are single rank... you can't mix ranks. Common HP OEM sources are Samsung/SKhynix/Micron:

16 GB example

2666 Speed

I hope this helps... and make sure to see the 2 attachments below.

EDIT: Regarding your other questions. I doubt from what you are doing that you need more than 32GB of memory, and I personally favor filling all available slots with identical memory. So, I'd use 8GB x 4 of 2400 speed HP memory for your new processor. If you truly need more then I'd shift to16GB x 4. You were gifted that very excellent workstation so hopefully you can feed it some $. Also, if you're not using a M.2 fast modern boot drive in a HP ZTD G2 card in the HP-recommended PCIe3 slot then that should get some attention next. There is more than enough on that here in the forum for you to do some reading on.

Good luck on your projects!

[BurningSoul1]

Thanks for report

Yes, there’s installed in pci slot nvme unit 500 GB. Is where windows is installed on, of course. 
There are 8GB from Samsung. They are pretty pricey though. Therefore would like to  install different brand. Ok I’d go with 4x8. 
in general must be enough if it technically corresponds to installed Moduls or am I wrong? Or do they have there some kind of block to generic Moduls?

[SDH]

When you use the official part number I provided for the 8GB sticks on eBay you'll see a number of memory suppliers... Samsung, SKhynix, Micron are common. Make sure you're looking at HP ones by presence of the HP part number on the sticker on the right hand side. Then you can also see the supplier's label on the left, with the vendor's codes on that. 

Yes, you can use those codes to search with also. No, there is no lock-out built in that prevents you from using memory that is recycled from another major source such as Dell, Lenovo, SuperMicro, etc. However, it is easier to just go for the ones originally from HP.

In earlier times HP "binned" their memory to higher than base specs and I would not be surprised if they still do that.  Mixing and matching modules from HP with the same HP bar code label supposedly is OK to do, but I prefer to not do that. For you I'd recommend not trying to become a master memory specialist for this small purchase.