Need Guidance on RAM Selection for Omen 880-139 Desktop

[hollang]

Ok, specs for this computer says the DRAM it supposed to come with 12 Gb of 288-pin UDIMM PC4-19200 DDR4-2400. The unit does indeed have 12 Gb of RAM. The spec books also say you can upgrade it with a combination of 4 & 8 GB UDIMMs. So, I naively went out and bought 2 x 8GB Crucial UDIMMs of the required  288-pin UDIMM PC4-19200 DDR4-2400 spec. Installed the new UDIMMs, but on power up I got 3 long/2short beep errors which research says indicates a memory problem.

So, I opened it up again & checked the seating of the UDIMMs, but they were solid. Then I looked more closely and see that the existing 12 GB is comprised not of PC4-19200 units, but PC4-2400, i.e., a Samsung M378A1K43CB2-CRC for the 8 Gb UDIMM and a Micron MTA4ATF51264AZ-2G3B1 for the 4Gb UDIMM. The new UDIMMS is a Crucial 2 UDIMM/16 Gb  kit product # CT2K864DFSB24A

Does the difference in the PC4 values (2400 vs 19200) account for the failure? Is there anything I can do other than buy more of the PC4-2400 or PC4-19200 so they all match ?

By the way, I pulled the 2 original UDIMMS (12Gb) and installed the 2 new UDIMMs (16 Gb total) and it works, showing 16 Gb available, so it's some kind of memory problem.  By the way, the memory slots have different colors, red and black. The order is red/black/red/black. The 2 original UDIMS were installed in the 2 RED slots so I assumed the upgrade needed to go in the 2 empty BLACK slots. Might that be a source of problem? 

Any advice appreciated as I think I may be able to return the 2 new UDIMMS to get a different spec if I act promptly.

[banhien]

@hollang 

Its specs

      https://support.hp.com/us-en/document/c05828859

They mean the same thing from two different angles Normal DDR4 ares

• DDR4-1600 (PC4-12800)
• DDR4-1866 (PC4-14900)
• DDR4-2133 (PC4-17000)
• DDR4-2400 (PC4-19200)
• DDR4-2666 (PC4-21333)
• DDR4-2933 (PC4-23466)
• DDR4-3200 (PC4-25600)

Your machine supports 32GB (4 x 8GB) max. You have to install in pair to get full benefit of dual channels 1 and 3 is one pair, 2 and 4 is another pair. Please use step 6 of the following guide

                 https://www.bhphotovideo.com/explora/computers/tips-and-solutions/installing-ram-desktop-pc

Regards.

[hollang]

Ok, I think I get it but confused why the mismatched original pair ( same speed but different Mfgrs & different capacities (4 & 8 FB) worked worked as it seems that’s not the recommended route. So, could I get by with 2 8 Gb sticks or do I need to fully populate each pair? If the latter, then I guess I only need to order 1more 8 Gb Udimm, right? Am I understanding it right?

[banhien · Accepted solution]

@hollang 

1.  As long as they are similar specs and within the parameters they can run even they come from 2 different vendors,

2.  You don't really to populate full pair but why you only have 1 leg.

3. You can keep old 8G and add 8GB to make a pair.

Regards.