A few months ago Amazon had a great deal on the Samsung 840 EVO SSD, and I took the opportunity to upgrade my aging MacBook Pro with it. Replacing the original hard drive was quick and easy, and the improvement in performance was obvious and profound. Anything involving disk access now seemed instantaneous. Soon after, I read on Anandtech that Samsung acknowledged a serious performance bug with the 840 EVO SSD that would dramatically slow down read performance for data that had not been rewritten in a while. The bug fix came out in October 2014, first as a Windows application, and with a Mac/Linux version promised by the end of October. As a Mac user I naturally waited until the Mac version came out and fortunately it became available for download a few days before the end of October.
You can download the Samsung Performance Restoration software from the Samsung SSD US Solid State Drive Downloads web page. Note that to fix the performance bug, you must download the updater from the “Samsung SSD 840 EVO Performance Restoration Software” section, not the “Samsung SSD Firmware Updates for Mac Users” section.
But the Mac updater came in a form I didn’t expect. While the Windows version is a point-and-click Windows application that lets you use the computer while it works in the background, the “Mac/Linux version” is actually a command line utility and has to be installed on a CD or USB drive that you can boot the Mac from. But the Mac version does not run under OS X, so you can’t use any solution that involves a drive that boots into OS X. That means you have to come up with a bootable non-OS X USB flash drive or CD, something that can be challenging for a computer user who has limited or no experience with a command line.
(Almost) creating a bootable USB flash drive with the fix
I first thought I could just download the “Bootable USB disk” version of the software (Samsung_Performance_Restoration_USB_Bootable.zip) and image it onto a USB flash drive. But the Samsung “Bootable USB disk” version isn’t actually bootable on a Mac from a USB flash drive. It contains only the Samsung utility, no bootable operating system of any kind. After looking up various instructions on the Web I was able to use Terminal to copy the image to a USB flash drive I formatted as MS-DOS FAT, but the drive was not visible in the list of volumes you get when you hold down Option while starting up a Mac, even after I found FreeDOS and added that to the disk image. A little more research revealed that you can’t boot a Mac from a USB flash drive unless it has the right EFI boot loader on it, and that isn’t included with either the Samsung updater or FreeDOS. You have to find the bootable USB flash drive software and figure out how to put it together on your own. Samsung actually warns you about this in the accompanying Installation Guide (PDF):
If you use a USB device 1) Please set your USB drive into a “bootable” state before starting the Performance Restoration software. 2) For assistance on completing this step, please refer to USB boot utilities from a trusted internet site.
Thanks a lot, Samsung. Basically this means if you don’t have the technical expertise to set up your own bootable USB flash drive, which usually requires Terminal commands, you’re out of luck with the USB flash drive option. (A couple months ago I successfully used the Terminal to copy another company’s DOS software onto a USB flash drive that did boot my Mac, but that’s because that company first made sure their disk image had everything necessary to boot a Mac. Samsung didn’t.)
While I’ve been using computers long enough to be the guy that my friends turn to for troubleshooting OS X and Windows and installing hardware upgrades, my Terminal skills are limited. I had already spent some time trying to figure out the bootable flash drive question and I probably could eventually, but after trying a few things that didn’t work I decided my time is better spent on other things. And I was thinking of all those other users who never even go near the Terminal: What should they do?
This is where I’ll ask for your help. If you know how to easily use OS X-based tools to create a bootable USB flash drive that can load a DOS-based (not OS X-based!) updater, or at least how to modify the Samsung or FreeDOS disk images so that the Mac can boot off it and the Samsung software will run, please post your instructions or links in the comments at the end of this article. Bonus points if it can be done with point-and-click (not Terminal) steps!
Update: Here is a possible solution. I haven’t tried it yet. Tutorial USB bootable SSD Firmware SAMSUNG 840 EVO (French, link is Google Translate for English). Also, readers are starting to add ideas to the comments, so check there too.
Creating a bootable optical disc with the fix on it
My MacBook Pro is old enough that it still has an optical drive, so I decided it was time to try the bootable optical disc option instead. I grabbed an old CD-RW (others have successfully used a writable DVD) and used the Quick Erase feature of Apple Disk Utility so that I could reuse it. Then I got ready to burn the Samsung ISO image to the disc. If you haven’t done this before you might find steps on the Web that tell you what Terminal commands to type, but I decided to see if I could simplify those steps far enough to avoid using the Terminal, and I was able to. The only software you need is Disk Utility, which is already on your Mac. These were my steps:
- At the Samsung downloads page, download the “Samsung_Performance_Restoration.iso” disk image.
- Rename the disk image filename extension so that the filename reads:
If you don’t rename the disk image, Disk Utility will just burn the single unopened ISO file onto the disk, and that’s not bootable. But when the disk image has a .dmg extension, Disk Utility will make the optical disc identical to the contents of the disk image, which is what you do want.
- In Disk Utility, choose Images > Burn, select “Samsung_Performance_Restoration.dmg” and click Burn.
- Put the blank optical disc in the optical drive and finish burning the disc. When you’re done it should look like this:
You can then continue below.
Running the update
Depending on the size of your SSD the update process may take an hour or two, and once you start it you must not interrupt the process. It shouldn’t erase data, but with an operation like this you never know. So before you get started:
- Back up the entire drive. If you are using Time Machine and its last backup was a few minutes ago, you should be set. Also, make sure you understand how to restore the entire drive from the backup.
- Run the fix only when you won’t need to use the computer for a few hours.
- If it’s a portable Mac, be sure it’s plugged into AC power since the process could take a long time to complete.
- If FileVault is turned on, turn it off. The tool won’t work if the drive is password protected. (An OS X user account password is OK, you don’t have to remove that.)
- Read the section “General Limitations” in the software’s Installation Guide for additional cautions.
To use the bootable media, insert it and then restart the Mac while holding down the Option key. This displays the list of connected bootable volumes. Select the volume with the update on it (in my case the CD) and press Return. (You should also be able to boot directly into a CD or DVD by holding down the C key as the Mac starts up.)
From this point on, the Samsung Performance Restoration utility takes over and works pretty much as it says in the Installation Guide. If you haven’t used DOS-based software, be aware that it’s all keyboard-based so forget about the trackpad or mouse, and pay attention for times when it asks you to do things like press the “y” (for Yes) key or press the Enter key.
The tool first installs a firmware update on the drive itself. When the tool says “Downloading Firmware…” I assume it means it’s downloading the firmware from the bootable media into the drive and not actually downloading over an Internet connection, but I’m not sure.When the firmware update is done, the software goes through a two-step process which includes recalibrating all the data on the drive. This can take a while and it depends on how big your SSD is. For my 1TB SSD, it took about two hours total. Do not interrupt the process. One odd thing is that the Start Date and Start Time on the screen were three hours ahead of the actual computer clock, I don’t know why.When it says “Samsung SSD 840 EVO Performance Restoration completed,” it’s safe to restart the Mac. At this point you can just hold down the Power button on your Mac until it turns off, then press the Power button again to start back up. If you want to eject the optical disc, hold down the mouse or trackpad button during restart and the Mac will pop out the disc before it even gets to the desktop.
If you want to read a more technical yet reasonably simple explanation of the bug, read the AnandTech article Samsung Releases Firmware Update to Fix the SSD 840 EVO Read Performance Bug. For even more detail about the bug, the solution, and the update process, I recommend the article Samsung 840 EVO Performance Restoration Tool preview – Getting EVOs back up to speed at pcper.com.
After the update
I was very relieved to find that the Mac rebooted right back into the regular OS X login screen and everything seemed to work just fine. Running the Samsung utility did not erase data, so I didn’t have to restore from a backup. I still took the precaution of running DiskWarrior on the SSD just to make sure the disk directory was OK (you can also use the Repair Disk feature of the First Aid tab in Disk Utility). Also, if you turned off File Vault as I did, remember to turn it back on.
Once you run the Samsung Performance Restoration software the fix is permanent, and you can’t run the updater a second time on the same drive, so you can go ahead and reformat and reuse the optical disc or USB flash drive you used to apply the Samsung Restoration software.
I know that optical drives are almost nonexistent in the currently available new Macs, so while the CD option worked for me I hope someone can shed light on how to create that bootable USB flash drive so that this article can be useful to more people.