During the last couple of weeks, numerous reports of Samsung SSD 840 and 840 EVO having low read performance have surfaced around the Internet. The most extensive one is probably a forum thread over at Overclock.net, which was started about month ago and currently has over 600 replies. For those who are not aware of the issue, there is a bug in the 840 EVO that causes the read performance of old blocks of data to drop dramatically like the HD Tach graph below illustrates. The odd part is that the bug only seems to affect LBAs that have old data (>1 month) associated with them because freshly written data will read at full speed, which also explains why the issue was not discovered until now. 

Source: @p_combe

I just got off the phone with Samsung and the good news is that they are aware of the problem and have presumably found the source of it. The engineers are now working on an updated firmware to fix the bug and as soon as the fix has been validated, the new firmware will be distributed to end-users. Unfortunately there is no ETA for the fix, but obviously it is in Samsung's best interest to provide it as soon as possible.

Update 9/27: Samsung just shed some light on the timeline and the fixed firmware is scheduled to be released to the public on October 15th.

I do not have any further details about the nature of the bug at this point, but we will be getting more details early next week, so stay tuned. It is a good sign that Samsung acknowledges the bug and that a fix is in the works, but for now I would advise against buying the 840 EVO until there is a resolution for the issue.

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  • chas_martel - Wednesday, September 24, 2014 - link

    Yes, I read that. Respectfully, that is not a "release" from the company. I was looking for something
    more "official", something that is kinda binding upon them. As it is now there is NOTHING from the company to the public. Samsung is not known for being communicative with their customers, IMO.
  • Gothmoth - Thursday, September 25, 2014 - link

    nobody spoke about that samsung HAS released it already.....
  • SputBob - Monday, September 22, 2014 - link

    Two weeks ago I fired up an old E8400 Core2Duo to do a Windows 7 update. It had been at least 6 months since I last turned it on. I have a 840 EVO as the OS drive. Seemed to take forever to bootup and I wondered what the heck had happened. I haven't messed with it since but it sounds like this is the problem.
  • trparky - Wednesday, September 24, 2014 - link


    Translated from German to English by Google...

    It seems that a firmware fix will be appearing for both the 840 and the 840 EVO on October 15th, according to the article linked above.
  • cpupro - Thursday, September 25, 2014 - link

    My not so old Samsung 500GB SpinPoint F1 HDD got CRC errors, but fortunetaly still works.
    My Samsung 20" SyncMaster 206BW monitor got vertical lines artifacts seen when is black sreen and black colour is also with artifacts.

    Only thing from you I have and which work is Samsung GT-S5230 cell phone.

    I don't count some ugly Samsung mouse which I also have.

    Now I read this.

    Nice job Samsung, I know that I will higly unlikely buy anything from you again.
  • johnyG.S - Thursday, September 25, 2014 - link

    Hello guys, like most here, also use an Samsung SSD 840 EVO 250, recently I heard this news, today I made a test to determine this problem reported by many!
    Link the images of the tests: http://imgur.com/a/wvjgf
    What do you think? Please.
  • poohbear - Saturday, September 27, 2014 - link

    Thank u for editing with an updated release date, & good thing samsung fixed it....october 15th cant come soon enough for those of us with the 840 evo as a system drive! I wonder how much this has effected sales as all the tech forums ssd/hdd sections on the net are abuzz with this. It was a really popular ssd back in the day...
  • xwingman - Sunday, September 28, 2014 - link

    When the firmware update fix becomes available will I need to reformat my drive and os then apply the fix? I tried doing an update a year ago with a kingston hyper ssd and it kept blue screening.

    I will be using this as a primary os drive or do you guys have any other options for a os ssd that won't need a fix at the moment?
  • AnonymousGuy - Tuesday, September 30, 2014 - link

    And this is why I only put Samsung drives in my secondary computers. Intel SSDs for when it matters.
  • sdr - Tuesday, October 14, 2014 - link

    I have an unboxed 500GB 840EVO. Hopefully SAMSUNG will release the fix October 15th (yes that’s tomorrow) as I have only one more week left to trade in the EVO for another product.

    If the fix is not released in the coming days then I will trade in for a 250GB 840PRO with proven track record and no reports about performance bug. That’s probably my best option?

    Hopefully SAMSUNG will also advise on the root cause of this performance bug and the way they have implemented the fix. More important will full speed be restored on old files and will the fix affect life-time of the SSD.

    I assume we have sufficient candidates here with 840 EVO disks and old data files that can validate the fix we are all waiting for.

    850PRO newest technology is advertised as ‘the way to go’ but I prefer to see some feedback from users and maybe in some months we can definitely say that 850PRO is the way to go.

    Let’s see ‘tomorrow’ if SAMSUNG can keep a promise and make the 840EVO a top-class SSD.

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