HP 840 G3 doesn't boot with 8GB RAM of KF426S15IBK2/16

[Mat3k]

I have HP Elitebook 840 G3. According to manual it supports up to 2 sticks of 8GB of DDR4-2133 RAM. I've replaced default single 8GB stick with one 8GB stick of Kingston KF426S15IBK2/16, which according to documentation, supports "JEDEC specification":

DDR4-2133 CL12-14-14 @1.2V

HP Elitebook 840 G3 doesn't boot with the new RAM. Could you explain why?

[resistencia]

Hi @Mat3k 

It is a Fury memory, compatible  BIOS with XMP, HP notebooks are not compatible with these memories can give results of lower frequencies or simply error and the laptop does not work.

KF426S15IBK2_16-B.ai (kingston.com)

[Mat3k]

Would you like to say that any RAM that have XMP profile embedded, is not supported, even if it also supports JEDEC profile, that is also supported by given HP laptop (PC4-17000/DDR4-2133 in this case)?

EDIT: Intel XMP FAQ says:

"Intel XMP memory modules will first boot with the default JEDEC settings. This ensures the first boot is successful even if the system does not support overclocking. After the first fail-safe boot, Intel XMP profiles can be selected in BIOS and applied to all subsequent boots."

In my understanding it means, that device shall boot (with one of JEDEC profiles supported by RAM and device), even if it doesn't support XMP.

[resistencia]

I ask you how do you match the CL of a normal memory with an XMP one? ,

I am telling you what your problem is, and the XMP in HP behave differently depending on the BIOS, in your case that is the problem, As a rule, you should not use XMP memory in BIOS that are not supported and even less with processors that do not support overclocking.

[Mat3k]

Based on my understanding, CL of memory is matched with CLs supported by BIOS based on SPD EEPROM entries of memory stick connected to motherboard. According to "SPD Annex L: Serial Presence Detect (SPD) for DDR4 SDRAM Modules, Release 3", published Sep 2015, Byte 20 (0x014) bit 5 set to 1 in combination with Byte 23 (0x017) bit 7 set to 0 means "CL 12 supported".

HP 840 G3 manual, referred in first post, does not specify which CAS latencies laptop supports, only "DDR4 PC4-17000 (2133 MHz) dual channel support". Shouldn't it be interpreted as: memory having any JEDEC specified CL of DDR4-2133 supported?

[Mat3k]

@Resistencia if HP 840 G3 doesn't support timings CL12-14-14 for DDR4-2133, which are set as supported in SPD of KF426S15IBK2/16 RAM, then what timings are supported by my laptop? Manual, as already mentioned, says nothing about timings. Where can I find such information?

[resistencia]

the CL is not the problem as you have indicated, it is already an XMP memory, you can continue arguing your way of seeing the problem, but I tell you that it is because XMP memory was used.

The proof is that the memory does not work. and normal DDR4-2133 memory does not exist but when they are not XMP the CL is 15 or 14

[TzortzisG · Accepted solution]

Hi Mat3k.

This is an old and known issue with these systems. You need flat 14-14-14 CL timings at the very least for the 2133 modules to actually work. These Kingston modules will generally default to the JEDEC timings, unless the laptop has a BIOS option to enable XMP. HP laptops generally don't have this option. The problem is not the XMP values, it's the 12-14-14 timings @2133 and the 14-16-16 timings @2400.

Read this discussion and open the links. You'll get all the information you need there.....

https://h30434.www3.hp.com/t5/Notebook-Hardware-and-Upgrade-Questions/Will-CL16-2400MHz-memory-work-... 

[Mat3k]

I couldn't find any CL14-14-14 module currently available for purchase (though I know they were available in the past, eg. Goodram  IR-2133S464L14S/8G), but found CL15-15-15 one (CMSO16GX4M2A2133C15) and I can confirm that it works.

P.S. If anyone would be able to check if any module with CL14-14-14 works with HP 840 G3 please confirm in reply. Extra points if the module has CL14-14-14 and some extra XMP profile (i.e. HX421S14IBK4/16) 😉

[TzortzisG]

Mat3k, cl15 is the Jedec standard, the absolute standard to be exact. You can also get away with cl14 because it is only a slight deviation (but still part) from the standard.

DDR4 SDRAM 

If you carefully read the thread I linked to in my previous post, I've personally used HX424S15IBK4/16 on very similar machines with good results. However, cl15 to cl14 doesn't really make that much of a difference. Running cl15 @2400 instead of cl17 @2400 does. For the kind of results you're going to get with the cl14 modules, it's not worth it.....