Will CL16 2400MHz memory work in Elitebook 840G5?

[atomich63]

I found a 32GB kit of G.Skill Ripjaws memory (https://www.amazon.com/G-SKILL-Ripjaws-PC4-19200-2400MHz-F4-2400C16D-32GRS/dp/B017UC3UPW/ref=sr_1_2?... )  rated at CL16 that costs no more than CL17 and am wondering if this will work optimally in an Elitebook 840 G5 at 2400MHz?  It has an 8th gen. CPU. 

[TzortzisG]

Atomich63, you should read these two threads about the Business Intel laptops with the results users got with cl15, cl16 RAM:

https://h30434.www3.hp.com/t5/Notebook-Boot-and-Lockup/Laptop-won-t-start-after-reboot-when-installe... 

https://h30434.www3.hp.com/t5/Notebook-Hardware-and-Upgrade-Questions/RAM-with-too-good-CL-for-HP-BI... 

[atomich63]

Thank you for your replies and those links.

What search string did you use?  I searched quite a bit and didn't come up with anything even remotely close.

[TzortzisG]

HP laptops have a long history of RAM compatibility problems. That's why on these boards you're likely to get advice about using the CRUCIAL site and buying the RAM it recommends, that's been checked by crucial and is guaranteed to work well.

This really became an issue with the arrival of the HX424S14 HYPERX IMPACT BLACK  modules with the cl14 latency when running at 2400MHz. It was superfast, and it was also cheap, so many people with laptops (including HP users) bought them to get the "BEST" ram for their systems. Unfortunately, HP laptops (especially the business line) refused to work with a latency that low (cl14). You'll see many threads about this issue in the HP forum, and I posted the two threads (relevant to this particular RAM) where users actually tried and tested different brands and latencies of RAM to see what they could get away with.

Another very interesting thread about this is https://h30434.www3.hp.com/t5/Notebook-Hardware-and-Upgrade-Questions/Kingston-RAM-not-correctly-det... where Huffer EXPERT Level 18 explains why HP laptops generally don't play well with aggressive RAM (usually gaming) modules......

On a side note, after the 2400 version of the Hyperx RAM, the following 2666 had equally "bad" timings with multiple JEDEC profiles and also failed to work on a lot of systems:

HX426S15  CL15-17-17@2666 - CL14-16-16@2400 - CL12-14-14@2133

From personal experience, if certain conditions are met, you can get away with using CL16@2400  on these professional HP laptops, and on occasion CL15@2400. I found a very rare kit of cl15 Hyperx RAM (HX424S15IBK4/64), that is deliberately "slow" due to the fact that it is meant for quad channel laptops, and upgraded two kaby lake probooks with them -they worked well. However, sometimes the laptops wouldn't boot on the first try, and I had to double-boot.

The real question is what you're hoping to gain out of using the slightly faster timed RAM.