Samsung’s 840 EVO update fixes slow reads with old data

Last month, Samsung confirmed that its 840 EVO SSD can suffer from slower read speeds with older data. The company promised to address the issue with updated firmware, and we’ve been experimenting with the fix.

Before we get into the results of our testing, we should spend a moment on the problem itself. Here’s how Samsung describes the issue:

SSDs usually calibrate changes in the statuses of cells over time via the flash management software algorithm. Due to the error in the software algorithm, the 840 EVO performed read-retry processes aggressively, resulting in a drop in overall read performance. This only occurs if the data was kept in its initial cell without changing, and there are no symptoms of reduced read performance if the data was subsequently migrated from those cells or overwritten.

Read-retry is used to compensate for changes in cell voltages, suggesting that voltage drift over time was a key factor here. The EVO’s flash management routines evidently haven’t been responding to voltage changes correctly.

Fixing the problem is a two-part process managed by Samsung’s appropriately named Performance Restoration tool. First, the utility flashes the SSD’s firmware with the new EXT0CB6Q revision. Then, it reboots the system and completes the restoration process, which we’re told involves “conditioning” the NAND. The entire process is non-destructive, so it shouldn’t compromise any data on the drive. It also only needs to be run once. That said, the target drive must have at least 10% free capacity for the tool to work its magic.

The data on the 840 EVOs we have in the lab isn’t old enough to be affected by the flaw. Fortunately, our resident developer, Bruno “morphine” Ferreira, has been running an 840 EVO 500GB in his personal system for more than 10 months. Having already noticed slower performance with older files, he bravely volunteered to test Samsung’s fix.

The restoration process went off without a hitch, though it took over an hour to condition Bruno’s drive. Read speeds seem to be much improved. Below is a screenshot from HD Tach, which tests read performance across the extent of the drive. Click the buttons below the image to switch between results from before and after the fix was applied.

Those dips before the fix correspond to performance slowdowns with older data. They’re nowhere to be found after the fix, where read speeds are much more consistent overall.

Samsung recommended running HD Tach to evaluate the fix, but we also had Bruno try SSD Read Speed Tester, which was developed specifically in response to the EVO issue. The graphs below depict the range of file read speeds based on the age of the data. Again, use the buttons to switch between the before and after results.

The differences here aren’t as striking, but there’s a definite improvement in read performance for older files. Some of the individual files load more than 2X faster after the fix, and one of them experienced a massive 6X speedup. Your mileage may vary, of course, but Samsung’s fix seems to work as advertised.

After applying the EVO update, Bruno also noticed snappier application load times. He says Windows now boots faster, too, particularly after it reaches the desktop and starts filling out the taskbar. We don’t have hard data on how the fix impacts load times, but OS and application files are likely to be older, so they’re good candidates for a speed boost.

Apart from addressing read speeds with older files, the new EVO firmware is supposed to perform identically to the previous release. Bruno ran a couple of quick CrystalDiskMark benchmarks before and after applying the fix, and the scores are pretty much identical.

Given how the bug manifests, we won’t know if the EVO is truly fixed until at least a month from now, when freshly written data will be old enough to exhibit slower read performance. Samsung is confident that the problem has been addressed, though, and the company has updated its validation procedures to look for similar issues in future products. For what it’s worth, Samsung says the problem is unique to the 840 EVO and not an artifact of that drive’s TLC NAND. The older, TLC-based 840 Series is unaffected, and so is the upcoming 850 EVO, which will use the three-bit version of 3D V-NAND.

If all goes well with final testing, the 840 EVO Performance Restoration tool will be released this week. There are still some associated caveats, like the updater not working with SSDs in RAID arrays or with older AMD SATA drivers, but those restrictions aren’t too different than those that typically come along with new SSD firmware. We’ll post a link to the update tool once it’s available.

Update — Samsung has released its Performance Restoration tool to the masses. The utility is available here, while the installation guide can be found here. Although the tool is Windows-only right now, a DOS-based version is coming before the end of the month. That release should allow Mac and Linux users to perform the update via thumb drive.

Comments closed
    • emphy
    • 6 years ago

    When can we expect this for the OEM version?

    I have the PM851 which has the same issue, with no word on when to expect an update and samsung’s contact page not working.

    • diesavagenation
    • 6 years ago
    • Mark_GB
    • 6 years ago

    I used this tool on my 1TB 840 EVO today, and everything went perfect. And yes, the system does feel much faster tonight.
    I am very happy with this drive, and its been the only drive in this computer since I built it back in April.
    I only wish I had more than one of them. And hopefully, I will have another before the end of the year.

    • ptsant
    • 6 years ago

    It can’t update the firmware with the AMD driver, even though I tried all methods of uninstalling and updating to the latest edition. I never had trouble updating firmware until now. Weird… I’ll have to wait for the DOS version.

    • DevilsCanyonSoul
    • 6 years ago

    I recommend that people try running the Magician Performance Test after applying this fix.
    I ran the fix, which took about 30 minutes to complete on a 1 TB Evo. Completed without losing data or experiencing any type of error code. Problem is, now when I run the Performance Benchmark inside of the Samsung Magician, it crawls so slow I have to cancel it out. Doing directory copies from a 840 Pro to the Evo now clock in sub-100 MB/sec.

    Something is borked !

    • TwoEars
    • 6 years ago

    Does it work with raid-0? got two disks in raid-0 and while i suppose I could backup the data, undo the raid, update the firmwares, re-image the raid-0 it would be easier if it just worked…

      • Nictron
      • 6 years ago

      No luck here. My drive is connected to Raid ISCI and it will not run. I will have to remove the drive and connect it to another PC with ATA and then run the tool. My performance has suffered over the last few weeks and I wondered why, now I know it was the EVO. My HDTach looks horrendous!

        • TwoEars
        • 6 years ago

        Scheise, but thanks for the feedback!

    • Inverter
    • 6 years ago

    Are there Mac or Linux versions of the tool?

      • cygnus1
      • 6 years ago

      Not yet. Their site reports a DOS version (I assume bootable) will be available by the end of the month for Mac and Linux systems.

        • just brew it!
        • 6 years ago

        Meh. Looks like I need to wait a couple more weeks or crack open a Windows system to move the drive to.

    • lethal
    • 6 years ago

    Here is the download link:

    [url<][/url<] I applied it and in my case the SSD had some truly atrocious speeds, which doesn't make much sense since the drive has barely two months of use. I restored a backup from my previous disk, so I'm guessing the graphs are reporting the file date and not when it was written on the disk. I used ssd speed reader to take a look at my read speeds [url<][/url<] Before: [url<][/url<] After: [url<][/url<]

    • wiak
    • 6 years ago

    sooo why is my 840 non-evo/non-pro/non-msata slow on read on older files then?

      • DancinJack
      • 6 years ago

      [quote<]Samsung has deployed three-bit TLC NAND in two generations of solid-state drives: the 840 Series and the 840 EVO. The value-oriented drives have been very popular, but they seem to have a problem. Scores of owners are reporting that older files have substantially slower read speeds than newer ones. The problem is detailed in several Reddit and forum threads, including this epic one over at It's on Samsung's radar, as well. The company provided the following statement when we inquired about the issue: Samsung recognizes the seriousness of any potential degradation of read performance on old data. We are testing and validating the circumstances that potentially cause this performance drop and will work diligently to resolve the issue.[/quote<]

    • mcnels1
    • 6 years ago

    I ran SSD Read Speed Tester on the 250GB 840 EVO in my laptop. Mine looks much worse than the example output in the article: most files older than 25 weeks old read at below 100 MB/s, with a very obvious downward trend as files get older. I need that new firmware!

    • wierdo
    • 6 years ago

    Wish there was an easy way to test for this in the endurance experiment, SSD data retention is a tricky beast to measure without a time machine.

      • meerkt
      • 6 years ago

      Supposedly higher temperatures can approximate accelerated aging.

    • kmieciu
    • 6 years ago

    Is this tool a Windows app or some kind of CD/USB bootable app?

    • stryfe
    • 6 years ago

    I have a strange issue myself I’m not sure if this is part of the issue or not but ever since last night certain sectors of my drive become unreadable. I would keep getting corrupted errors 0x800 exceptions, etc. I’m going to try this fix tonight after I reload my system and see if it makes any difference. But this isn’t too re-assuring considering I got another evo siting right in front of me. :-/

      • morphine
      • 6 years ago

      Check that you’re using the latest version of your SATA controller’s drivers.

      About a year ago, I had “bad sectors” with Win8 + Intel RST drivers, which… weren’t.

    • Firestarter
    • 6 years ago

    I hope that they hurry up and release this so I can go fix 2 EVOs this weekend (that I had my father and brother buy)

    • tbone8ty
    • 6 years ago

    Amd sata drivers are all old lol

    • Stickmansam
    • 6 years ago

    I’m hoping they’ll address the 840 as well as my testing as well as many others show the drive suffers as well

    • ronch
    • 6 years ago

    I’ve been waiting for this. Thanks for the heads up, Geoff.

    • Arvald
    • 6 years ago

    even in Samsung Magician I can see the performance degradation… any word on when other than soon?
    They did say the 15th so it has got to be soon

    • willmore
    • 6 years ago

    I’m very curious to see if this helps drives hold their performance with time or if this is going to be an every 6 months kind of thing.

    Edited to add:
    Over at PCPerspective, they mention that the tool will only run *once* and any one drive. So, that rules out running this tool six months from now. I guess that says that Samsung seems confident that this is a final solution.

      • MadManOriginal
      • 6 years ago
    • JustAnEngineer
    • 6 years ago

    I’ll have to give this a shot on the 1 TB 840 Evo in my ultrabook.

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