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Have you noticed your Solid State Drive (what’s an SSD? How Do Solid-State Drives Work? [MakeUseOf Explains] How Do Solid-State Drives Work? [MakeUseOf Explains] Over the past few decades, there has been a considerable amount of work in the field of computer hardware. While computer technology is constantly improving and evolving, rarely do we experience moments where we simply... Read More ) suffering from slipping performance? If Samsung made your drive, it probably employs “Triple Level Cell” (TLC) NAND memory modules. A bug afflicts most–if not all–TLC drives. Fortunately, Samsung made a fix available for one of their drives to Windows users.

The problem: After 9-40 weeks, the SSD’s legendary speed can fall beneath even platter-based hard drives. After delays and failure, Samsung now claims it eliminated the bug with its latest firmware update.

On the downside, this update can function only on Windows or OS X systems. For those with Linux, you might update the drive from a Windows or Mac computer; although Linux users suffer from another deal-breaking issue with TLC memory.

What Is TLC memory?

Before Samsung’s invention of Triple Level Cell solid state memory, two kinds of memory dominated consumer and enterprise markets: Single Level Cell (SLC) and Multi Level Cell (MLC) memory.

SLC offers performance advantages at the expense of price and storage capacity. MLC memory offers cheaper costs while storing twice as much data per cell. Triple Level Cell (TLC) stores three times as much data as SLC and offers even cheaper costs to manufacture than MLC.

All flash memory comes with the disadvantage of limited write endurance – the more data written to memory, the faster the drive wears out, leading to its eventual failure. While flash memory can take a tremendous amount of writes before dying, manufacturers oftentimes void the drive’s warranty after a fixed (and very low) number of writes.


Unfortunately, unlike SLC and MLC, TLC memory suffers from an even lower write endurance, although this limitation only impacts those with overly stringent warranties.


How do I know if I have a TLC Drive?

There’s no comprehensive list of drives afflicted by the bug. This proves especially problematic for Ultrabook owners, who may not know whether TLC NAND inhabits their device. The surest method (in my experience): Check in Windows Device Manager and locate the entry under hard drives.

First, go to Device Manager:

device manager

Last, go to Hard Drives:

finding the name of the drive in windows


Then search the Internet for the name of the drive, including the term TLC. In my case, I would search for PM851, including the term TLC.

search for pm851

Users can also test their device’s read speeds for signs of decline. However, it seems that all TLC drives decline over time. The speed at which they decline centers around the production process, or how small the individual memory cells are. 19nm cells decline in speed after the data inhabiting the cells reaches 9 weeks. The older 21nm cells decline after 40 weeks.

For those interested, currently hosts a tool custom designed for testing read speeds relative to age, which is evidence of the bug. I ran the application (after malware-scanning it) and the results strongly suggest that the Samsung PM851 SSD (in most Ultrabooks) suffers from the bug.

overclock tool run on pm851

You will notice that older files are read more slowly than newer ones, on average.

A Brief History of Buggy TLC SSDs

Samsung’s lack of transparency compounds matters. At first, Samsung claimed the bug afflicted only the 840 EVO line of SSDs. However, subsequent drive speed readings indicated the Samsung 840 (but not the Pro line) suffered from the issue. Later on, reports emerged that the PM851 SSD used in most Windows Ultrabook Dell XPS 13 2015 Review and Giveaway Dell XPS 13 2015 Review and Giveaway The XPS represents the pinnacle of laptop design in 2015, and it's the best bang for your buck out of any laptop we've ever seen in the $800 price range. Read More s may also suffer from the problem.

The most recent rumors suggest that perhaps even the Samsung 850 EVO line, which employs V-NAND TLC, also suffers from performance issues. If true, then the sluggish performance may relate to electron decay and current leakage, a shortcoming exacerbated by TLC’s storage of 3 bits per cell.

Here’s a partial list of drives probably afflicted the by bug:

  • Samsung 840
  • Samsung 840 EVO
  • Samsung PM851 (M.2 form factor, limited to Ultrabooks)

Samsung hasn’t yet announced fixes for all these drives, yet. In fact, it seems their updated firmware includes only the 840 EVO line, despite the problem’s proven (and unacknowledged) existence on the 840. Of particular interest: The MP851 M.2 form factor SSD inhabits many Ultrabooks (what’s an Ultrabook? What Is An Ultrabook & Can It Succeed? [Technology Explained] What Is An Ultrabook & Can It Succeed? [Technology Explained] Remember when the word laptop described virtually every mobile computer on the market? The choices were certainly easier back then (because there was simply less choice available), but today there’s a far wider variety including... Read More ), including the Lenovo Yoga Pro, the Microsoft Surface, and the Dell XPS series (and a lot more).

To my knowledge, none of these manufacturers pushed out Samsung’s fix yet, although Dell’s latest firmware update was released in April of 2015, making it the latest firmware update available. If you feel like rolling the dice, you can download and install the firmware update here. It probably won’t resolve the issue. It also may end up causing serious damage, if you do not have a compatible system.

angles dell xps 13

Applying Samsung’s TLC Fix for the 840 EVO

The fix only works on Windows systems. To install it, you must download the Magician software and update your drive’s firmware. Unfortunately, Samsung’s Magician is not available to those using M.2 form factor Ultrabooks.

Samsung provided a series of firmware upgrades, the first of which failed to resolve the issue. The second firmware upgrade requires more explanation. Essentially, Samsung’s firmware upgrade rewrites each bit stored on your hard drive, imperceptibly when your computer rests.

While this method maintains the SSD’s peak read performance, it will incur additional wear and tear. This additional wear and tear will void Samsung’s warranty far earlier than expected on the drive. Also, because TLC’s maximum write endurance falls substantially short of MLC drives, the fix falls short of user expectation.


Keep in mind that even TLC memory offers great resistance to memory writes, so the fix won’t break your drive anytime soon. Even so, consider disabling hiberate on SSDs Disable Hibernate On Your SSD For Warranty Purposes Disable Hibernate On Your SSD For Warranty Purposes Killing your SSD only requires a bit of laziness. You can preserve your warranty and extend your SSD's lifetime by turning off hibernation. We show you why & how to do it. Read More .

Linux Concerns

Note that if you own a Linux system, a bug exists which can destroy your data. The problem extends from Samsung’s failure to properly implement TRIM (what’s TRIM? Why TRIM is Important to Solid State Hard Drives? [Technology Explained] Why TRIM is Important to Solid State Hard Drives? [Technology Explained] Read More ) for use with Linux systems. An additional bug can actually destroy a Samsung laptop, if users install Linux, although the issue may have already been corrected as of the publication date of this article.


While Multi Level Cell (MLC) memory’s reliability ranks high, Samsung’s TLC lacks the same reputation. It seems that Samsung rushed TLC to market before performing proper validation testing. As a result, TLC–and possibly its successor V-NAND TLC–possess serious bugs that Samsung hasn’t fully resolved yet.

The simplest solution is to avoid any products that include TLC NAND memory until the problems get ironed out. Those owning an 840 EVO will need an immediate answer. You may want to consider installing the fix, despite the increased writes to your drive. For everyone else, you will need to wait.

Have you noticed decreasing performance of your SSD?

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