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REVIEW / Samsung 840 Evo 120 GB

TLC NAND for a lower price tag

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Pierre-Jean Alzieu Published on September 9, 2013
Translated by Hugh Ehreth


  • Capacity
  • Cache 256 MB
  • Read speed 540 MB/s
  • Write speed 520 MB/s
  • 4K random read 94000 IOPS
  • 4K random write 35000 IOPS
The Samsung 840 Evo is the successor to last year's Samsung 840. And like its predecessor, this SSD was not made to compete with the best of the best. Samsung's real goal here is reasonable price. To keep costs down, the company opted for TLC NAND, a type of flash memory that's economical, but less reliable over time (1,000 cycles) than the MLC NAND found in the 840 Pro (3,000 cycles, not to be confused with the 840).

Each capacity of the 840 Evo is advertised as having 540 MB/s read speeds. As for the write speeds, it depends on the size of the drive. The 120 GB model allegedly has a write speed of 410 MB/s, three times as fast as its predecessor, and the others (250 GB to 1 TB) write at 520 MB/s.


The Samsung 840 Evo is a 2.5" drive with a SATA III interface (6 Gbps). Its 7-mm-thin body is lighter than most, weighing 44 grams, an undeniable plus for laptop owners.

Samsung used its own MEX Controller, which is composed of three ARM Cortex-R4 cores clocked at 400 MHz, whereas the previous MDX Controller in the Samsung 840 was clocked at 300 MHz. The TLC NAND uses a 19 nm process.

Just as SanDisk did with the Extreme II and Ultra Plus, Samsung used a buffer system (TLC flash simulated as SLC, with one bit instead of three) to boost the write speeds. The buffer size varies depending on the SSD's capacity: 3 GB for the 120 and 250 GB, 6 GB for the 500 GB, 9 GB for the 750 GB, and 12 GB for the 1 TB.

To protect data against temperature increases, Samsung also included a system that curbs the read/write speeds in order to keep the drive under a certain temperature, or at least to limit its overheating.

Data Transfer Speeds

Samsung 840 Evo 120 GB - speeds

File Transfers (Photos, Videos...): Sequential Speeds

The speeds Samsung advertises are accurate when it comes to large files. We measured 503 MB/s read and 416 MB/s write speeds. The Samsung 840 Evo gets better speeds than last year's 840, but it's still a good notch below the 840 Pro 256 GB, our current record holder.

That's with files smaller than the buffer. If you transfer files over 3 GB in size, however, the transfer rate plummets to 260 MB/s—the same as last year's 840.

Accessing Programmes: 4K Random Access

Small files are handled better than large files. With 64 MB/s writes on 4K files and 33 MB/s reads, it's on par with the outstanding Samsung 840 Pro.

Samsung SSD Magician

Samsung Magician

Also in the box is a CD for SSD Magician, or you can download it from Samsung's website. This is an intuitive programme that offers a variety of functions, such as system info, benchmarking, SSD/OS performance optimisation, firmware updates, secure deletion and over-provisioning.

In the CD you'll also find a cloning programme for transferring data from another drive to the SSD. It's quick and easy to do, perfect for when you want to replace your old drives!


  • 506 MB/s reads on large files
  • 416 MB/s writes on large files
  • Lightweight, perfect for a notebook
  • Samsung SSD Magician software is handy and intuitive


  • TLC flash memory is theoretically three times less long-lasting than MLC
  • Write speed drops to 260 MB/s on files over 3 GB


The Samsung 840 Evo definitely isn't the best SSD we've reviewed, but it's relatively fast and lightweight and it costs less than most higher-performance drives. The biggest drawbacks are that it uses TLC flash memory, which doesn't last as long as MLC, and only has a 3-year warranty where high-end models are usually guaranteed 5 years.
3 Samsung 840 Evo 120 GB DigitalVersus 2013-09-09 12:21:00
Compare: Samsung 840 Evo 120 GB to its competitors
Store Available Price £ 61.00 See offer  
Currys 70.00 See offer  
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PC World 70.00 See offer  
Pixmania 78.00 See offer  
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