Samsung 840 EVO mSATA Review: 120, 250, 500, And 1000 GB, Tested

Results: 128 KB Sequential Performance

Fantastic sequential read and write performance is a trademark of modern SSDs. To measure it, we use incompressible data over a 16 GB LBA space, and then test at queue depths from one to 16. We're reporting these numbers in binary (where 1 KB equals 1024) instead of decimal numbers (where 1 KB is 1000 bytes). When necessary, we're also limiting the scale of the chart to enhance readability.

128 KB Sequential Read

Samsung's four mSATA-based 840 EVOs top 500 MB/s with just two outstanding commands. Read performance, despite three-bit-per-cell NAND, remains a strength. These are the kind of numbers we'd expect from the 840 Pro, but it's more surprising to see coming from the company's 840 and 840 EVO. Still, with sequential reads, we'd be concerned if performance wasn't this high.

128 KB Sequential Write

Sequential writes are where we see the benefit of more dies. As capacity shifts from 120 to 1000 GB, write performance increases substantially. Admittedly, Samsung's Turbo Write technology does affect the outcome by using some of the MLC as emulated single-level cell flash. And of course, the larger models have more of this faster space at their disposal. Because this is how we test, the results end up quite favorable for Samsung. But expect minimum performance (what you'll see once the cache limits are surpassed) to be a good deal lower. 

Here's a break-down of the maximum observed 128 KB sequential read and write performance with Iometer:

The 840 EVO mSATA drives manage respectable finishes in our sequential performance testing. Demonstrating very similar read speeds, positioning in this chart comes down to the results of our write testing. Not only does write performance scale with the number of dies, but Samsung's Turbo Write cache size increases with capacity, too. That means the 1000 GB model with 12 GB of cache is able to post particularly impressive write numbers, exceeding 500 MB/s. 

Even the modest 120 GB drive, with just eight die, achieves more than 200 MB/s in our write benchmark. Once the Turbo Write cache is filled, you'll see the 120 GB 840 EVO drop to 130 MB/s or so. And in that product's case, a scant 3 GB of cache fills up a lot more quickly. Even still, the benefit is tangible in real-world measures of performance. 

Although Turbo Write complicates our results, it's a solid technology. Moreover, it's now one of several SLC emulation systems in use. SanDisk's nCache is one of the originals, but Toshiba, OCZ, and now Samsung employ mechanisms that are not entirely dissimilar. As you can see, benchmarking and explaining results gets tougher. But their utility does translate into real-world performance improvements. Particularly when you're talking about the smaller drives equipped with fewer dies, the speed-up is meaningful.

  • vaughn2k
    Now all we need is the price to drop, then I'll get one.. ;)
  • blackmagnum
    Maybe it's time to upgrade the HD of an old working notebook to SSD! But will a Core2Duo processor bottleneck a SSD?
  • jrharbort
    @blackmagnum: You don't have to worry about your processor being a bottleneck, but rather, your system's SATA interface. It is highly doubtful that your Core 2-based notebook (much like my own) has an m-sata slot, and the 2.5" bay for a HDD would have a SATAII port, not SATAIII. So the overall max read/write rates would be cut in half. But to answer your question in another way, tom's posted an article almost a year ago on the subject of upgrading older systems with an SSD:,3469.html
  • spookyman
    @blackmagnum: You be glad to upgrade your hard drive to a SSD drive. Did it for my goddaughter's after she had a hard drive crash and it runs a lot faster then before.
  • JohnnyLucky
    Interesting article. It coincides with the current shift from desktop pc's to mobile pc's.
  • nekromobo
    But aren't we already moving to M.2. Why can't I buy Samsung XP941 :(
  • pyro226
    "The latest version offers RAPID support to non-EVO drives like the 840 Pro."Got my hopes up there. The standard 840 series SSDs are NOT supported. The article didn't explicitly state they were, but what other drives (aside from the 840 Pro and EVO) have Rapid support? Perhaps "The latest version offers RAPID support to both EVO and 840 Pro SSDs." would be more accurate.
  • LordConrad
    "This company has a track record of disrupting the markets it enters; now that it's focusing attention on smaller form factors with enthusiast-class hardware, it's only a matter of time before we start seeing M.2-based offerings as well."This is mainstream hardware, I don't know any enthusiats who will settle for drives with TLC NAND.
  • lowguppy
    It is nice to see these finally available. I've been watching the Crucial m500 mSATA drive for a while, and the 480gb version frequently falls under $300 on NewEgg, which is competitive with 2.5" SSDs.
  • RedJaron
    12750948 said:
    This is mainstream hardware, I don't know any enthusiats who will settle for drives with TLC NAND.
    "Enthusiast" to me doesn't automatically mean getting the fastest, biggest, bestest, craziest parts regardless of price. It also means people who put a lot more thought into their systems and thoroughly weigh all their options. MLC, TLC, or not, the fact remains that the EVO is a fast, reliable drive for a good price.

    Your argument sounds similar to, "I don't know any enthusiasts who will settle for LGA 1150 instead of LGA 2011," or "I don't know any enthusiasts that would settle for a non-K CPU."