Looking at the specs, the 256 GB model should be almost 25% faster at sequential writing and 20% faster at launching and installing applications. Everything else about the 256 GB model is identical to the 128 GB version. It uses MLC flash memory, offering 3,000 or more possible P/E cycles, and a 300 MHz triple-core Samsung ARM9 controller.
Note that Samsung also makes a 512 GB model of this solid state drive that's identical to this 256 GB SSD.
Samsung 840 Pro Series (512 GB)
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Samsung is the only brand that builds every piece of its SSDs, from the controllers (MDX) and memory to the software.
The 840 Pro comes with a five-year warranty, which is rare in the world of consumer electronics. It uses MLC memory, with a lifespan announced at 3,000 P/E cycles per cell before any stability issues should arise. That may look a little low, but when you think about it, for 8 hours of use per day with 10 GB of data written and erased on average, that makes for an estimated lifespan of 105 years!
Unlike certain competitors, the 840 Pro is a straight-forward SSD with no extra functions to help boost data transfer rates. There's therefore no over-provisioning (although this can be activated via the Samsung SSD Magician software included, see below), there's no on-the-fly compression and no system for writing to the top layer of the memory cells. This was clearly visible from the consistency of the results seen with the HD Tach Pro benchmark. In other words, the read/write speeds remain relatively constant while the drive fills up all of its 256 GB of memory.
Data Transfer Speeds
File transfer (photos, videos, etc.): sequential data transfer rates
In optimal conditions (with low-level formatting), the read speeds with this SSD are identical to those of the 128 GB model, with a 517 MBps sequential read speed with large files in our benchmark test and 484 MBps in practice. These are the best performances we've seen on the market so far.
In write mode, we measured 500 MBps with the benchmark test. As surprising as it may seem, the write speeds measured in practice turned out to be much higher, measured 645 MBps when copying files manually. That's 130 MBps faster than the 128 GB Samsung 840 Pro and 240 MBps faster than the 240 GB Intel Series 520 Cherryville—the two highest scoring SSDs in this field so far.
For installing and launching applications, this SSD works at a similar speed to the 128 GB version. It's actually better (5 % to 10% better) than other SSDs equipped with competitor controllers and/or compatible only with SATA 2.
Accessing programs: 4K random access time
Random access speeds are a bit less impressive. With 64 MBps in write mode with small files (4 KB) and 33 MBps in read mode, speeds are within average. Still, these results are much better than what you'd get with a classic HDD.
Samsung SSD Magician Software
This Samsung solid state drive comes with SSD Magician software. This easy-to-use program offers information on the system, performance benchmarking, SD/OS optimisation, firmware updates, secure erasing and over-provisioning. Note that Samsung doesn't have its own software for the "Disk Clone" function, and instead suggests downloading Norton Ghost 15.
You may be interested to know that the SSD we tested—one of the first models off the production lines—gave up the ghost not long after our tests. The first 840 Pro 256 GB drives manufactured had known reliability issues, but this has since been fixed by Samsung. In fact, readers using newer versions of this particular SSD haven't reported any such problems.