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Similar specs
Despite their differences, the Crucial M500 960GB and Samsung 840 EVO 1TB have quite a lot in common. Their flash is built on similar fabrication technologies, for example. The EVO's flash is fabbed on a 19-nm process, while the M500's is made with 20-nm technology.

Also, both drives have 128Gb (16GB) NAND dies that double the capacity of the 64Gb (8GB) dies commonly found in other SSDs. These 128Gb dies are key to reaching terabyte territory. They're also a liability for the lower-capacity models. The M500 240GB and 840 EVO 250GB use only 16 dies each, but 32 dies are required to take full advantage of the internal parallelism in their respective controller chips. That's why those models have lower write performance ratings.

With 64 dies apiece, the 960GB and 1TB variants have more than enough flash to saturate their controllers. The M500 uses a Marvell 88SS9187 chip, while the EVO sports a proprietary Samsung MEX design. Both controllers have eight parallel NAND channels.

Crucial deploys the M500's NAND across 16 physical packages, while Samsung squeezes the same capacity into just eight. The 840 EVO's circuit board is smaller as a result, though the cases are the same size. Each one measures 7 mm thick, allowing the drives to slip into slimmer notebook bays.

Speaking of notebooks, the 840 EVO 1TB is also available in mSATA form. Crucial doesn't have a bite-sized version of the M500 960GB, though. The M500's mSATA and M.2 flavors top out at 480GB.

When Samsung introduced the 840 EVO mSATA, it released new firmware for the 2.5" version. This revision enables support for the TCG/Opal and IEEE 1667 encryption standards required by eDrive, Microsoft's hardware-accelerated BitLocker implementation for Windows 8. The Crucial M500 has supported eDrive since its debut, so the EVO is a little late to the party. In fact, its eDrive firmware was originally scheduled for September. Better late than never, though.

Accompanying software
Software may be a secondary concern for solid-state drives, but there's a big difference between what comes with the M500 and 840 EVO. The M500 drive is a barebones affair. There's no accompanying Windows utility, and cloning software is only available with an installation kit that's sold separately.

Samsung's Magician utility and data migration software can be downloaded by any 840 EVO owner. The cloning tool is designed specifically for migrating from larger mechanical drives; it allows some data to be transferred to secondary storage rather than the target SSD, which is almost always smaller than the source hard drive. Then there's the Magician utility, which can download and apply firmware updates, optimize system settings, monitor drive health, and read SMART attributes, among other things.

I'm not sure I trust the Magician utility's general health indicator—it's been far too optimistic about the state of the 840 Series drive in our endurance experiment. However, I do like how the main interface displays the total number of bytes written. Users still have to dig into the SMART data to track the number of bad blocks, but at least that's easily done with through the Magician utility.

Third-party software is required to get similar information out of the M500. Even then, it's not that simple. Check out the SMART attributes exposed by Hard Disk Sentinel, the utility we've been using to monitor wear in our endurance experiment:

The reallocated sector count adds up the number of bad blocks. There are no attributes for tracking writes, though. One of those vendor-specific attributes can probably be translated to total bytes written, but I wouldn't trust an unlabeled attribute, and I'm surprised that such important information is obfuscated in the first place.

TR reader Karol tipped me off about the fact that the M500 does tally the number of logical sectors written in its extended SMART device statistics. Those stats aren't accessible with common utilities like HD Sentinel. However, they are available via Smartctl, a command-line tool included in the free Smartmontools package. Getting a bead on total writes shouldn't be this difficult, but at least it's possible.

Crucial should really develop a Windows utility with basic monitoring capabilities. An integrated firmware updater would be nice, too. Samsung's Magician software displays a notification when new firmware is available, and it handles both downloading the update and installing it.

The Magician utility also has a feature called RAPID mode, which uses a slice of system memory as a high-speed drive cache. We took a closer look at RAPID mode in August, and the caching solution did improve performance in some benchmarks. However, it slowed the EVO in other tests, and we're not crazy about writes being cached in volatile DRAM. Unless you're looking to set benchmark records, we recommend keeping RAPID mode disabled. The EVO is fast enough without it.