Review: Samsung's most affordable, triple-level cell SSD

This TLC SSD rivals two-bit MLC SSDs in performance and blows them away in price

Samsung's 840 EVO SSD is the company's second-generation 3-bit MLC SSD, and it's one of the most affordable, high-quality drives on the market today.

The 840 EVO SSD, Samsung's densest-capacity, consumer solid-state drive, comes with upgraded firmware and the company's fifth-generation MEX 5 multi-core controller, which offers more clock speed than its predecessors.

The new processor boasts 400MHz clock speeds, compared with 300MHz in previous generations, so it's about 33% faster. That faster clock speed translates into a 27% increase in the number of input/output operations per second (IOPS), according to Samsung.

The company has also advanced the signal processing in the controller -- a move that's designed to ensure that the higher-density drive keeps the same level of endurance and reliability as Samsung's previous SSDs.

Lower pricing

But the big deal about this SSD is its price -- it costs less than competing products, and less than previous Samsung offerings. The new 1TB model can be purchased through online sites such as Pricegrabber.com for $599. The 750GB and 500GB models sell for $493 and $350, respectively. The 250GB and 120GB models sell for as low as $191 and $99, respectively.

The Samsung 840 EVO SSD
The Samsung 840 EVO SSD.

The previous-generation 840 SSDs have a retail price of $109 for a 120GB model, $200 for a 250GB version, and $449 for a 500GB model. (See prices of competing SSDs in the chart below.)

The EVO SSD comes with a SATA III (6Gbps) interface. The 2.5-in. SSD offers what Samsung calls ultra-low power consumption that helps extend laptop battery life. Samsung achieves lower power usage by placing the SSD in "idle mode" when it's not being used, thus maintaining a lower power use profile "99.5% of the time" when it's not being actively used, according to Chris Geiser, Samsung's senior product manager of memory and storage systems.

But I've found over years of testing that SSDs have little affect on a laptop's battery life. Monitors use far more power than drives, especially solid-state drives. What SSDs do offer is read/write performance that's vastly superior to that of hard drives; they're also more durable than hard drives, making them well suited for use in mobile devices like laptops.

The new 840 EVO SSD features some significant changes from its 840 SSD predecessor. For one, the NAND flash has dropped in size from 21-nanometer processing technology to 19nm, so more data can be crammed into each chip.

Samsung also doubled the cache from 512MB in the previous model to 1GB DRAM in the new SSD. The added DRAM is more about managing a new multi-threaded and multi-core controller, according to Geiser. Unlike previous-generation SSDs, the 840 EVO can read and write data while it is performing "garbage collection" operations in the background. Garbage collection is the act of deleting blocks that were previously marked for erasure.

The new EVO SSD also boasts two new capacities over its 840 SSD predecessor; it's available in new 750GB and 1TB versions.

Also boosting the performance of the SSD is something Samsung calls "Turbo" technology. Turbo basically designates an unused portion of the SSD as a higher-performance buffer; it simulates a natively higher-performing single-level cell (SLC) NAND flash drive. For example, the 1TB 840 EVO SSD can set aside 36GB of NAND flash capacity to act as a 12GB buffer that acts as higher-performance SLC memory.

"By doing that, we're eliminating a lot of the overhead, a lot of the error correction that's required in order to be able to use 3-bit MLC NAND, and consequently can write cache much more quickly," said David Lin, vice president of product management at Nvelo, a Samsung subsidiary responsible for writing caching software.

According to Samsung's specification sheet, the 840 EVO SSD's Turbo function significantly boosts write speeds, which can be a weak spot for some SSDs.

SSD Performance Comparison Chart

Samsung 840 EVO SSD Seagate 600 OCZ Vertex 450
Tested capacity 500GB 480GB 256GB
Price $350 ($199 for 250GB) $410 ($209 for 240GB) $260 ($499 for 512GB)
Boot-up time 25 sec. 12 sec. 13 sec.
Max. read time (4K blocks) 508MB/sec. 514MB/sec. 469MB/sec.
Max. write time 488MB/sec. 443MB/sec. 355MB/sec.
2GB file transfer 8 sec. 8 sec. 10 sec.
Shutdown time 13 sec. 25 sec. 25 sec.
Restart time 36 sec. 35 sec. 37 sec.
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