Remember Intel's old X25-M SSD? The drive came out in 2008 and played a big role in seeding a solid-state storage revolution that continues to sweep across the PC industry. SSDs have come a long way since those early days, when the X25-M 80GB was considered a relative bargain at $600. That worked out to seven dollars per gigabyte, a far cry from the sub-$1 prices that have democratized the technology in recent years.
There is perhaps no better illustration of how far we've come than Crucial's new M500 SSD. For the same $600 asking price as the old X25-M, one variant of the M500 delivers a staggering 960GB of storage. Do the math, and you're looking at 63 cents per gig—an order of magnitude reduction in cost. How's that for progress?
Fittingly, these lower prices have been driven in part by cooperation between Intel and Micron, Crucial's parent company, who collaborate on NAND production through a joint venture dubbed IM Flash Technologies. IMFT fabbed the 50-nm flash chips for the X25-M, and it has since moved to finer process tech at 35, 25, and now 20 nanometers. Each new process packs more gigabytes per wafer, increasing bit densities and decreasing prices.
While the M500 960GB represents a sort of pinnacle for SSD progression, its $600 price tag is still rather steep. The 240 and 480GB versions are more affordable, and those are the ones we've gathered to review today. As you'll see, there's much more to the M500 than its peak capacity.
Meet the new flash
As you've probably deduced already, the M500's MLC memory chips are built on a 20-nm manufacturing process. There's a difference between this NAND and what's lurking inside Intel's 20-nm 335 Series, though. The memory chips in the Intel and most other contemporary SSDs weigh in at 64Gb (8GB) each, while the M500's NAND chips have twice that capacity.
This is the first drive we've seen with 128Gb NAND, and the shift has interesting implications. For one, it makes hitting higher capacities possible with fewer dies, which is probably part of the reason the 960GB drive costs much less than its terabyte-class peers. Having fewer dies isn't always better, though. SSD controllers rely on parallelism for maximum performance; past a certain point, drives with fewer NAND dies are actually slower.
With most SSDs, performance starts to fall off at capacities below 240-256GB, suggesting that current controllers favor 32-die configurations. That makes sense, since most controllers have eight channels and can address four chips per channel. The M500 240GB uses only 16 flash dies, and its performance specifications reveal that configuration isn't ideal.
|Capacity||Die config||Max sequential (MB/s)||4KB random (IOps)||Price||$/GB|
|120GB||8 x 128Gb||500||130||62,000||35,000||$130||$1.08|
|240GB||16 x 128Gb||500||250||72,000||60,000||$210||$0.88|
|480GB||32 x 128Gb||500||400||80,000||80,000||$395||$0.82|
|960GB||64 x 128Gb||500||400||80,000||80,000||$600||$0.63|
To see the M500's full performance potential, you'll need at least the 480GB version. The 240GB model has a much slower sequential write speed rating, and its random I/O rates are lower, as well. The 120GB drive is slower still, with only one NAND die for each of the controller's eight channels. No wonder Crucial is skipping a 60GB variant.
There's no difference in the performance ratings attached to the 480 and 960GB models, though. Also, note how the per-gigabyte price goes up as the drive capacity drops. Somewhat surprisingly, the 960GB drive delivers the best value of the bunch; it's the only one that dips close to 60 cents per gig. The prices for the other models are nothing special.
Beneath its grey metal exterior, the M500 is anchored by a Marvell 88SS9187 controller chip. This is an eight-channel design with, you guessed it, four chip-enables per channel. The controller combines a dual-core CPU with a 6Gbps SATA interface and support for DDR3 cache memory. It also has a built-in RAID engine and hardware support for 256-bit AES encryption.
The RAID engine works in conjunction with RAIN, a flash redundancy scheme that's also employed by Micron's enterprise-grade SSDs. This mechanism reserves a portion of the flash for parity data, which is why the M500 series has somewhat lower capacities, similar to those of SandForce-based drives.
Crucial also takes advantage of the Marvell controller's encryption hardware. The M500 supports the TCG Opal 2.0 and IEEE 1667 standards, making it compatible with the BitLocker encryption built into Windows 8. This is the first SSD we've seen with explicit support for Win8's encryption tech.
In addition to protecting bits and bytes from prying eyes, the M500 guards against data loss due to unexpected power failures. See all the little capacitors in the bottom right corner of the circuit board pictured above? Those store enough power to allow the M500 to shut down gracefully if the lights go out or your battery dies.
Speaking of mobile applications, the M500 comes in a slim 7-mm form factor compatible with thinner notebooks. The drive still has the standard mounting holes used by all 2.5" notebook drives, and Crucial includes an adhesive-backed spacer to ensure a tight fit in 9.5-mm notebook bays. Versions of the M500 with even smaller mSATA and NGFF M.2 form factors are also in the works, although they'll be limited to 480GB and smaller capacities.
To deal with cramped notebook internals that have little airflow, the M500 employs an adaptive thermal management system. If the drive temperature exceeds 70°C, "NAND operations" are reduced by "approximately 40%" until thermals return to normal. This throttling doesn't affect the speed of the SATA link, but it will lower overall drive performance.
Like most consumer-grade SSDs, the M500 is covered by a three-year warranty. Crucial says the drive can withstand 40GB of writes per day for five years, which works out to 72 terabytes—plenty for even relatively heavy use. It's worth noting that this endurance specification is considerably more optimistic than the one slapped on Intel's 335 Series SSD. That 20-nm drive is only rated for 20GB per day for three years, or 22TB in total.
The effects of cell degradation and interference are more pronounced on NAND chips built with finer fabrication processes, so the M500's generous endurance rating is certainly comforting. Unfortunately, there doesn't appear to be any way to monitor flash wear or how many bytes have been written to the drive. Unlike rivals Intel and Samsung, Crucial doesn't provide utility software with a built-in health indicator. The M500's payload of SMART attributes doesn't contain any references to flash wear or bytes written, either. Several of the SMART attributes are labeled "Vendor-specific," but you'll need to guess what they track and read the associated values using third-party software.
Without accompanying software, the M500's overall package feels especially spartan. It doesn't help that the drive is shipped without the 3.5" bay adapter commonly included with 2.5" SSDs. That plastic spacer is the only other thing in the box.
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