Ram installation problem, hp g4 z4 i9

[BunsenBurner]

@SDH yes, ram was in the machine when I bought it. I have 2 x 16gb installed and works fine. The ones I bought on Amazon are 16gb too but 3200 mhz. Original set up is 2 x DDR4, 16gb  Samsung 2666 (1333 MHz) installed in first two slots, which is why I thought 4x 16gb would be okay. S

I returned the ones I bought and plan to try 4 x these, DR4-2666MHz PC4-21300 CL19 1.2V UDIMM 288 Pin Unbuffered Non ECC, 16gb.

[SDH]

It would be helpful to see pics of what you have that worked and also what your new ones are. Sometimes it is very evident what the mismatch is from pics to someone with the right number of failures under their belt.

At the very least try to match the OEM codes on the label on the left. Another approach is that if you have an Assembly HP part number from a HP label on the right to try to match that with your new ones. In the past HP has said that if you get matching Assembly part numbers even sticks from another OEM source should work.  Yours is a particularly picky workstations/processor one, however.  On the OEM part number after the hyphen the first few alphanumerics count (as you may have seen from the PDF above) but the ones after those don't count... they usually have to do with site of manufacture.

[BunsenBurner]

Thanks. Later, I'll take out the ram that's currently in already and post a pic if I can. 

In the mean time, this is what I get from speccy:

slot 1
DDR4
Size 16384 MBytes
Manufacturer Samsung
Max Bandwidth DDR4-2666 (1333 MHz)
Part Number M378A2K43DB1-CTD
Serial Number 4192BC86
Week/year 48 / 18

slot 2:

Type DDR4
Size 16384 MBytes
Manufacturer Samsung
Max Bandwidth DDR4-2666 (1333 MHz)
Part Number M378A2K43DB1-CTD
Serial Number 4192865E
Week/year 48 / 18

There are 8 ram slots

[DGroves]

the ram you mentioned  (samsung Part Number M378A2K43DB1-CTD) a 16GB dimm is no longer being produced

https://semiconductor.samsung.com/us/dram/module/udimm/m378a2k43db1-ctd/

i strongly recommend you visit the memory venders link

i provided to find compatible ram  that is guaranteed to work

[BunsenBurner]

Thanks I'm checking this page 

https://semiconductor.samsung.com/us/support/tools-resources/product-finder/?tabname=dram

Confused about the organisation part. Should I be looking at 2G x 8 for this ram?

[SDH]

You want to match the 16GB sticks you already own (based on the Samsung part code you provided above).

Below are two example pics of that specific Samsung memory, HP RAM from eBay, which are the same sticks as yours. Note that these show two different HP Assembly P/Ns on their right-side HP label (which is not an issue). Thus, you can search eBay for M378A2K43DB1-CTD or L04430-501 or 933278-001 and find the Samsung ones that match the left side label on the ones you own and know work. The rank is "2Rx8". I'd personally want ones that have one of the HP Assembly part numbers shown on the HP bar code label, but you might choose to just search for that Samsung part number.

Good luck on your project.