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Samsung's 840 Pro Series SSD reviewed

The real 830 Series successor stands up

Samsung's 830 Series has been our favorite SSD for the better part of a year now. We gave the drive our coveted Editor's Choice award when we reviewed it, and we've been recommending the thing ever since. Can you blame us? The 830 Series combines excellent all-around performance and solid reliability with a price tag that won't break the bank—or at least it did. Recently, prices have risen steadily as the drive's online stocks have dwindled. Some models are no longer available from major vendors, and before long, eBay will be the only way to get an 830 Series SSD delivered to your door.

Our old favorite is disappearing from online listings because it's being replaced by a new generation: the 840 family. Samsung has a two-pronged attack this time around. At the low end of the market, the 840 Series targets budget-conscious consumers. For those who crave performance, there's the 840 Pro Series.

Although they're based on the same controller technology, the 840 Series and its Pro sibling are very different animals. The 840 Series uses TLC NAND, which has slower write performance and shorter endurance than the MLC flash found in most consumer grade SSDs, including the old 830 Series and the new 840 Pro. Despite its more professional moniker, 840 Pro is the 830 Series' true heir.

Unlike those obsessed with Kate Middleton's baby bump, we don't really believe in birthrights around here. If the 840 Pro wants to claim daddy's crown, it's going to have to go through all the other SSDs on the market right now. We've tested the 840 Pro against more than a dozen contemporary counterparts to see where it stands, and you might be surprised by the results.

Somehow more professional
On the surface, the 840 Pro closely resembles the 840 Series. Both models use the same 7-mm case, enabling compatibility with slimmer notebooks that can't accommodate traditional 9.5-mm drives. Notebook users should also be impressed by the 840 family's light weight; the 840 Pro weighs just 53 grams, which is noticeably lighter than all the other SSDs that have passed through our labs (apart from the similarly feathery 840 Series).

The 840 Pro and 840 Series look similar on the inside, too. Their circuit boards appear almost identical, save for minor differences in the markings on the controller chip and flash packages. Both drives use the same Samsung MDX controller, though. Like the MCX chip in the 830 Series, the MDX controller has three cores based on the ARM architecture. Those cores are clocked at 300MHz, up 80MHz from the old MCX chip. While the 6Gbps Serial ATA host interface remains unchanged, the eight-channel flash interface has been upgraded to support version 2.0 of the Toggle DDR NAND standard. The gen-two spec supports transfer rates up to 400 MT/s, providing three times the per-die bandwidth of Toggle DDR 1.0.

Apart from higher clocks and support for faster NAND, the MDX chip looks a lot like its predecessor. The controller can scramble the bits stored on the 840 Pro using a 256-bit AES encryption algorithm. There's no compression trickery involved, so the drive should offer consistent performance regardless of the data type. Samsung hasn't implemented a flash-level redundancy scheme, either. While the lack of RAID-like protection makes the 840 Pro vulnerable to data loss in the event of a physical NAND failure, Samsung doesn't have to devote a portion of the drive's storage capacity to parity data. As a result, the drives are available in 128, 256, and 512GB capacities instead of the 120, 240, and 480GB flavors typical of SSDs with die-level redundancy.

Our 256GB drive packs 32 individual NAND dies spread across eight physical packages. There are four dies per package, with each die weighing in at 8GB. Samsung manufactures the NAND itself, and these particular chips are built on a 21-nm fabrication process. The 830 Series uses 27-nm NAND.

Fabbing flash on a smaller process node allows Samsung to squeeze more dice—and more gigabytes—onto every wafer. The higher bit density should lower the all-important per-gigabyte cost, but there is a string attached. As the process geometry shrinks, so does the number of write-erase cycles that the NAND can endure. Samsung hasn't revealed how many cycles its 21-nm flash can survive, nor has it published a total-bytes-written specification detailing the volume of host writes the 840 Pro can withstand. Fortunately, we can take some comfort from the fact that Samsung selects only the most promising flash chips for the 840 Pro. The drive is also covered by a five-year warranty, providing additional peace of mind.

Capacity Die config Max sequential (MB/s) 4KB random (IOps) Price
Read Write Read Write
128GB 16 x 64Gb 530 390 97,000 90,000 $150
256GB 32 x 64Gb 540 520 100,000 90,000 $270
512GB 64 x 64Gb 540 520 100,000 90,000 $600

The longer warranty helps to justify the 840 Pro's premium price tag. Expect to pay around $270 for the 256GB version we've been testing. That price works out to over a dollar per gigabyte, which is relatively high by today's standards. The 256GB model does occupy the sweet spot in the 840 Pro lineup, though. The 128 and 512GB versions both cost more per gig, and the former has a substantially lower sequential write speed rating. Looks like the MDX controller needs to be attached to more than 16 NAND dies for optimal performance.

To further entice buyers, Samsung has combined the 840 Pro with a downloadable copy of Assassin's Creed III. Bundling a video game with a solid-state drive might seem a little unusual, but it's nothing new for Samsung. You may recall that the 830 Series was sold with Batman: Arkham City. Assassin's Creed costs $60 right now, so it's not a trivial extra.

If you're not much of a gamer, the 840 Pro does come with other software. Samsung includes its own Magician utility, which lets the user secure erase his drive, monitor its health, update the firmware, and adjust the over-provisioning percentage, among other functions. The 840 Pro ships with an older version of the Magician software, but we've been playing with a new beta that features a revamped interface:

The new look is cleaner, and I like the fact that the volume of bytes written is displayed up front. I do wish the health status were more descriptive, though. Telling me the drive is in "good" shape doesn't provide any information on how long it'll stay that way. The SMART variables accessible via the Magician software aren't of much help on that front, either.

One feature missing from the new Magician app is a tab for data migration, which used to lead to a message saying that copies of Norton Ghost were included only with drives sold as part of upgrade kits. Samsung has its own data migration software for drives sold without accompanying upgrade kits, although it oddly wasn't included on our 840 Pro's software CD. A free copy can be downloaded from Samsung's site, and it transferred our test rig's Windows install to the 840 Pro without fuss. The migration software only works with Samsung SSDs, though.