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HP Recommended
EliteBook 840 G5
Microsoft Windows 10 (64-bit)

New EB 840 G5 with 256 GB Toshiba NVMe drive KXG50ZNV256G.  Specs for drive show Seq Read speed up to 2,700 MB/s and Seq Write speed up to 1,050 MB/s.  Testing with CrystalDiskMark 6.0.1 gives Seq Read very close to the 2,700 MB/s, but the Seq Write is only 345 MB/s ... significantly lower than its potential rating, and even slower than a SATA3 drive.


I've run the test several ways and this seems to be the result each time.  The computer came with the C: drive partition encrypted by BitLocker, so I thought it might have been the encryption process slowing it down.  But, the HP recovery partition, 😧 drive, an 18 GB partition with >2 GB of free space and not BitLocker encrypted reads the same read and write speeds.


EB 840 G5 has:

i7-8550U CPU

8GB DDR4-2400 RAM

Model:  3RF14UT


Update: through further investigation I found this review of an EB840G5 with the same Toshiba NVMe drive, EB840G5 Review.  They too report speeds like I am seeing.


Given the read speeds, it would appear the hardware platform is allowing for the data rate, so perhaps the drive is not living up to its write specifications?  The drive I have has the same firmware as that in the review.


Update 2: this same issue has been in Dell forums for some time.  The firmware on my drive is AAHA4102.  Dell has updated to 4104 and 4105.  I can't determine from their forums yet if the 4105 release fixed the slow write.  For fun, I downloaded their 4105 release to see if the Toshiba untility would see my drive.  It does see it, but confirms the Dell firmware update is not compatible with my drive.  (The Dell firmware is AADA4105 ... so I'm willing to guess the "D" and "H" in the fimrwares may mean Dell and HP).


Anyone else with an EB 840 G5 with either the 256 or 512 GB Toshiba KXG50ZNVxxxG drvie that could share their results?




HP Recommended

I continued to study to see if it is the drive or the system.  IT at my spouse's company loaned me a 512 GB NVMe Samsung 970 Pro to try.  Specs for this drive are Seq Read 3500 MB/s and Seq Write 2300 MB/s.  Speeds using this drive at different stages of Windows install and update are:


Fresh install of Windows, no updates yet:

Seq Read: 2460 MB/s, Seq Write: 2309 MB/s


Complete rounds of Windows Update until Up To Date:

Seq Read: 3527 MB/s, Seq Write: 2347 MB/s


Install Samsung NVMe Driver:

Seq Read: 3515 MB/s, Seq Write: 2348 MB/s

(many of the random tests improved with Samsung driver)


Turn BitLocker Encryption for C: Drive:

Seq Read: 3530 MB/s, Seq Write: 2355 MB/s


Results seem to suggest the EliteBook 840 G5 platform is plenty capable in supporting solid data rates for an NVMe drive.  It seems to point to the Toshiba drive as the limitation.  This is consistent with findings from the Dell forum too.


HP Recommended

Today, tested Toshiba KXG50ZNV256 drive in desktop PC (having H87 Chipset, i7-4790, 16 GB DDR3-800, Win10 Pro). Results were Seq Read 2800 MB/s, Seq Write 1085 MB/s ... exceeding the drive specifications of 2,700 MB/s and 1050 MB/s. Seems drive is capable of its specifications. Because we can see the EB 840 G5 is capable of high NVMe speeds, and the Toshiba Drive is capable of its rated speeds, there must be something interacting between the two that is limiting write performance as a system.  I've submitted a case into HP MySupport to help resolve.

HP Recommended

Unbelievable.  I entered most of the details from above into a ticket.  HP's response:


"Regarding NVMe drive, please use the below link and check:


Really, at every turn I mention it is a Toshiba KXG50ZNV256 drive, and am directed to Intel SSD downloads.  At least they could suggest to me with Intel SSD download I should get for the Toshiba product.


Back into the ticket system to try to get some support.

HP Recommended

I can confirm that KXG50ZNV256G seq write performance degrades terribly over 3-4 days and only ~100GB written.

out of the box the write speeds were 1.01GB/s, after win install, conf and some tests... only 62-350MB/s.

(ATTO 4.00.0f2 4K+)


after using (Sysinternals) sdelete.exe -z c: write speeds went back 1.01GB/s but not for long.


tested on two HP Probook 650 G4 Notes, both behave the same.


terrible drive, totally untested by HP (and also by Dell).




HP Recommended

Thanks for diving into this, it is the same stuff that I saw on my Surface Laptop 2.  These drives are, for some reason, of lower quality than the ones we can buy.  I will pull it out and put in a generic 512Gb that I had great success with in the past.  Mind you that the write speed on Sequential at Q32T1 4KiB at Q8T8 and 4KiB at Q32T1 are pretty much the same which leads me to believe the drive is not optimized from a hardware point of view.  It is a PCIe 3.1 3x4 capable bus so I would certainly expect better write rates.  That being said I know that manufacturers try to cut cost as much as possible. 

HP Recommended

I have the Toshiba KXG50ZNV256G in the 256 GB variant installed in a HP Omen 880 as the system drive.

The drive has a Seq Read speed of 2,500 MB/s and Seq Write speed of around 320 MB/s while the specs for the drive promised around 1000 MB/s.

  The reason appears to be the SLC cache in the drive being filled by the operating system, in my case Windows 10. See for example this Tweaktown article.


A workaround is to get another NVMe drive as system drive and use the Toshiba drive as drive D:, doing that and running Optimise Drive in Windows 10 on the drive restores the speed around 1000 MB/s for writes. I think HP cut a few too many corners on this one, as you dont expect your system drive to go from 1000 MB/s down to around 300 MB/s in the course of a few days.


So the tl;dr of it all is:

* Get another system drive.

* Use the Toshiba as secondary drive and all is well.

† The opinions expressed above are the personal opinions of the authors, not of HP. By using this site, you accept the <a href="https://www8.hp.com/us/en/terms-of-use.html" class="udrlinesmall">Terms of Use</a> and <a href="/t5/custom/page/page-id/hp.rulespage" class="udrlinesmall"> Rules of Participation</a>.