450 G9 - RAM Compatibility issues

[Ancient_One]

Our company has a reasonable number of ProBook 450 G8/G9 notebooks, however a few new users need additional RAM (16GB original HP ->32GB), so I bought extra 16GB modules from Crucial. The ProBooks were brand new out of the box.

I've upgraded plenty of Elitebooks (G5/G6 primarily) in my time, but not ProBooks, so this makes me wonder if anyone else has come across this.

I checked the Crucial site and selected the 16 GB module that were flagged as compatible with my ProBooks. When I installed the module into the first notebook, I got a POST RAM error (three long beeps, two short beeps). Swapped the memory modules around, and confirmed that the original module, and the replacement module (1 x 16GB) both worked fine (boot to Windows OK) in the notebook on their own, but not together. Then I grabbed a second Crucial module and confirmed that two Crucial modules together (2x16GB) worked fine together as well in the notebook. Second check in another notebook had same result - POST RAM error when mixed, but OK singularly.

I then checked the existing HP supplied module in the first notebook, and found it was a Dual Rank module from Samsung. The Crucials on checking were single rank. Checked the second notebook and it was also a dual rank module. I checked my own ProBook, and the module is a single rank module from SK Hynix. Installed the Crucial stick (2 x 16GB) and it booted just fine.

Guess the question is are the ProBooks that much more sensitive to memory mixing than the Elitebooks? I've never worried with Elitebooks and they just work, If they are more sensitive, then I'll have to crack each one open and check the existing module, before even ordering more RAM, which is a load of extra work.