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Review: Samsung SSD 840 EVO (120GB)

by Parm Mann on 25 July 2013, 13:01

Tags: Samsung (005935.KS)

Quick Link: HEXUS.net/qaby3v

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And here we were, staring multiple SandForce drives in the face, thinking solid-state innovation had ground to a halt. How wrong we were. Boffins at some of the biggest names in the industry have proven that there's plenty of room for improvement, with Intel introducing a new level of consistency across the SATA 6Gbps interface and Crucial showing us that high-capacity SSDs needn't cost the earth.

Up next? Samsung, who's here to tell us that affordable, low-capacity drives don't have to offer second-rate performance when compared to larger drives in the same range. It's a familiar problem, and one what does need tackling. Take the recently launched Crucial M500 as an example - great drive, but the low-cost 120GB model takes a 68 per cent performance hit in terms of sequential write speed when compared to the range-topping 960GB drive.

It's that massive gap that Samsung is attempting to narrow with the new 840 EVO. Designed as a successor to the popular 840 Series, the EVO drive slots in below the top-of-the-line 840 PRO and aims to offer an affordable upgrade path to those looking to take their first steps into solid-state territory. At launch, the EVO Series drive will be available in a choice of 120GB, 250GB, 500GB, 750GB and 1TB capacities, with prices ranging from £87 to £510.

Samsung SSD 840 EVO Series

Samsung 3-core MEX Controller
19nm Samsung Toggle DDR 2.0 NAND Flash Memory (400Mbps)
Onboard DDR2 Cache
SATA 6Gb/s, compatible with SATA 3Gb/s and 1.5Gb/s
Sequential Read Speed
up to 540 MB/s
up to 540 MB/s
up to 540 MB/s
up to 540 MB/s
up to 540 MB/s
Sequential Write Speed
up to 410 MB/s
up to 520 MB/s
up to 520 MB/s
up to 520 MB/s
up to 520 MB/s
Random IOPs (4KB Reads, QD32)
up to 94,000 IOPs
up to 97,000 IOPs
up to 98,000 IOPs
up to 98,000 IOPs
up to 98,000 IOPs
Random IOPs (4KB Writes, QD32)
up to 35,000 IOPs
up to 66,000 IOPs
up to 90,000 IOPs
up to 90,000 IOPs
up to 90,000 IOPs
Dimensions (LxWxH)
100 x 69.85 x 6.8 (mm)
Active Power Consumption
0.1W Typical
Idle Power Consumption
0.045W Typical
Life Expectancy
1.5 million hours Mean Time Between Failures (MTBF)
72TB total bytes written (TBW), equal to 40GB per day for 5 years
3 Years
Retail Price Basic
w/ Laptop Kit
w/ Desktop Kit

The read and write speeds of the spacious 1TB drive are rated at 540MB/s and 520MB/s, respectively, but what's interesting is that the cheap-and-cheerful 120GB model isn't far behind - it claims to offer 540MB/s reads and 410MB/s writes, which is impressive for a low-capacity drive.

So how has Samsung managed to loosen the previously tight link between performance and capacity? As we know, today's SSDs utilise multi-channel controllers and are able to offer optimal performance when numerous NAND memory chips are interfacing with the processor in parallel.

Taking a look inside the 120GB EVO SSD suggests that the problem should, if anything, be exaggerated. Samsung has just a pair of 19nm NAND memory chips (one either side of the mini-PCB) hooked up to a triple-core controller and a modest 256MB onboard DDR2 cache.

Creating all the components in-house is an obvious advantage - they should work in harmony when set to task by Samsung's proprietary firmware - but two NAND chips, a multi-channel controller and a small DDR2 cache is hardly a recipe for blazing speed. There has to be something else afoot, and there is; both in terms of hardware and software.

First and foremost, Samsung has increased the speed of the controller. The new chip, dubbed MEX, is based on the same triple-core ARM Cortex R4 architecture, but is now clocked at 400MHz; a full 100MHz faster than the previous MDX. A bump in core frequency is typically the way to increase performance, but the 840 EVO's real party tricks are two new technologies dubbed TurboWrite and RAPID (Real-time Accelerated Processing of I/O Data) Mode.