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Intel's second-generation X25-M solid-state drive

More than just a 34nm die shrink

Given the firm's expertise in both storage controller design and semiconductor fabrication, it was probably only a matter of time before Intel got into the solid-state storage business. The chip giant finally burst onto the SSD scene a little less than a year ago with the introduction of its X25-M line of 2.5" multi-level cell (MLC) flash drives. A performance revelation at the time, the X25-M easily captured the SSD performance crown. In fact, one could argue that it's still the SSD to beat, even today.

Much has changed in the 11 months since the X25-M's initial launch, though. Samsung has a new SSD design that's being sold by Corsair and OCZ, and it offers better sequential throughput than the X25-M in both synthetic benchmarks and with real-world file operations. A Korean firm by the name of Indilinx has also introduced a Barefoot SSD controller that's being used by nearly half a dozen drive makers. The Indilinx has been quite popular in certain circles, and with strong random-write performance and the promise of TRIM support for Windows 7, it's become an intriguing alternative to the X25-M.

Intel has been busy since the X25-M's launch, too. In November of last year, it unleashed a single-level cell (SLC) version of the X25 geared toward enterprise environments. A line of 1.8" X18-M SSDs also joined the family. More recently, in April, Intel released a firmware update to improve the long-term performance of its X25-M and X18-M models. All along the way, Intel has aggressively cut prices. The 80GB X25-M initially launched at just under $600. Today, it costs close to half that.

SSDs remain an expensive proposition, even for enthusiasts accustomed to paying top dollar for high-performance hardware. Prices continue to plummet, though, spurred most recently by Intel's introduction of a new generation of X25-M drives based on 34nm fabrication technology. These new units are much cheaper than their forebears, with the latest 80GB flavor selling for just $225 in bulk quantities—35% less than the street price of the old X25-M. And it gets better, because Intel says these latest models are even faster than the originals. One arrived at our doorstep this past Wednesday afternoon, and we've been testing it since. Let's see what we've learned.

Subtract 16 nanometers
Because solid-state drives are essentially just arrays of flash memory chips, the best way to decrease their cost is to move to finer fabrication technologies that squeeze more gigabytes onto each silicon wafer. The original X25-M's MLC NAND flash memory chips were fabbed using 50nm process technology, but the new models have flash chips built with 34nm tech. As a result, there's more storage per chip in the new drives. The X25-M debuted at 80GB with 20 flash chips weighing in at 4GB each. This time around, the X25-M line is led by a 160GB model packing a whopping 16GB per chip.

The second-generation X25-M's storage controller is also fresh silicon, but there's been no die shrink here. Instead, Intel has removed any and all traces of halogen from the chip, which should appeal to laptop makers looking to boost their Greenpeace ratings. According to Intel, the controller's architecture is on the same "technology node" as the original, so it's still a 10-channel design. Interestingly, however, the company wouldn't reveal whether the new chip runs at a higher internal clock speed than its forebear.

In fact, the new X25-M's cache memory has actually gotten slower. The new drives have 32MB of 133MHz Micron DRAM, up 16MB but down 33MHz from the first-gen X25-M. The 32MB cache is still much smaller than what's strapped to new SSDs based on Indilinx designs, which use 64MB DRAM chips, and the latest Samsung controllers, which come with 128MB of cache.

Intel does say that latencies have been reduced throughout the updated storage controller. As a result, the drive's random read latency has been reduced from 85 to 65 microseconds, while its random write latency has dropped from 115 to 85 microseconds. That's about a 25% improvement on both fronts, which suggests an internal clock speed bump.

X25-M X25-M G2
Controller Intel PC29AS21AA0 Intel PC29AS21BA0
Flash fabrication process 50nm 34nm
Capacity 80, 160GB 80, 160GB
Cache 16MB 32MB
Max sequential reads 250MB/s 250MB/s
Max sequential writes 70MB/s 70MB/s
Read latency 85 µs 65 µs
Write latency 115 µs 85 µs
Max 4KB write IOPS 3,300 8,600 (160GB)
6,600 (80GB)
Max 4KB read IOPS 35,000 35,000
Active power consumption 150 mW 150 mW
Idle power consumption 60 mW 75 mW

In addition to reducing latencies, speeding random writes seems to have been another focus of Intel's performance optimizations. The company claims that the new 80GB X25-M can push up to 6,600 random 4KB write IOPS—double the original's theoretical peak and 2,000 shy of the 8,600 IOPS claimed for the new 160GB model. The X25-M's peak random read rating hasn't increased, though; it's still sitting pretty at a staggering 35,000 IOPS.

Although the X25-M's random write performance has apparently been improved, it doesn't appear that much has been done to hasten sequential transfers. The gen-two unit's still saddled with its predecessor's relatively sluggish 70MB/s sustained write speed rating. That rating wasn't particularly impressive when the X25-M first launched, and with Indilinx- and Samsung-based drives boasting sustained write speed ratings in the 200MB/s range, it's a glaring potential liability now. Intel says sustained write speeds haven't increased because it was concentrating on making a quick transition to 34nm flash and driving down drive prices, instead. That may be the most prudent approach. After all, we've found that the original X25-M is no slouch when it comes to real-world write performance. We'll see how this latest spin fares in a moment.