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A mostly refined package
Although Intel got its start in the SSD business using proprietary controller technology, third-party tech can be found in most of its SSDs today. The 330, 520, and now 335 Series all use the same SandForce SF-2281 flash controller. This chip was first unveiled in February of 2011, and it seems to have left behind the firmware-based BSOD issues that plagued its early life. Intel has only been selling SSDs based on the SF-2281 since February of this year, when the 520 Series made its debut.

If you've been following the SSD scene, you should be familiar with the SF-2281. The chip pairs a 6Gbps SATA interface with eight individual NAND channels. Unlike most SSD controllers, it doesn't require separate cache memory. The chip's internal buffers are large enough to take care of business without resorting to an external DRAM cache.

The defining characteristic of SandForce's controller technology is DuraClass, a black box of technologies that includes a funky write-compression scheme dubbed DuraWrite. SandForce has kept the inner workings of DuraWrite close to its vest, but we know that it uses lossless, on-the-fly compression to reduce the flash footprint of incoming writes from the host. By writing less data to the flash, DuraWrite aims to increase the longevity of the NAND while also improving performance.

Flash memory, of course, can withstand only a limited number of write-erase cycles. The less data is written, the fewer of those cycles are consumed, and the longer the flash should last. Writing less data should also take less time, resulting in higher performance. DuraWrite's potential benefits are bound by the compressibility of the data being written, though. Data that's already been compressed or is highly random in nature has less to gain from SandForce's bit-scrambling mojo than, say, a repeating pattern of bits and bytes.

DuraClass also includes a hardware encryption engine, but the Intel 335 Series' product documentation makes no mention of encryption support. Encryption support is nowhere to be found in the supporting materials for the 330 Series, either, but it is a prominent feature of the 520 Series. Incidentally, Intel had a hand in uncovering a flaw in the SandForce controller's 256-bit AES encryption. As a result, the 520 Series' encryption support was downgraded from 256 to 128 bits.

RAISE is another component of SandForce's DuraClass special sauce. This RAID-like redundancy scheme is designed to protect against physical flash failures; typically, it can keep the drive's data intact after the demise of an entire flash die. RAISE is supported on higher-capacity models in the old 330 Series, and it appears to persist in the 335 Series.

The 335 Series actually lacks lower-capacity models entirely. In fact, the 240GB model is the only member of the line. Intel expects this to be the most popular capacity, and given current prices, it's hard to argue with that sentiment. 240-256GB drives tend to offer the lowest cost per gigabyte right now. Intel plans to "evaluate demand" before committing to adding other capacities to the 335 Series. In the meantime, the 330 Series will continue to be sold.

As you can see in the picture above, our 335 Series sample looks a little bit rough. The top of the drive's case is unblemished, but the bottom looks like it just got kicked out of Chris Brown's Lamborghini. This isn't a one-off offense, either; we've seem similarly beaten-up panels on Intel's 320 and 520 Series SSDs. Intel says the cases meet its fit and finish requirements, which are apparently pretty lax on the finish front.

The case conforms to the 9.5-mm version of the 2.5" form factor used by typical SSDs. Most notebooks can accommodate 9.5-mm drives, but it's worth noting that the 320 and 520 Series use slimmer cases that can slip into 7-mm bays. Each of those drives comes with a screwed-on spacer that beefs up the thickness to 9.5 mm. Oddly, that spacer moves inside the case for the Intel 335 Series.

Popping open the case also reveals the circuit board, which is loaded with 16 NAND packages. There are eight packages per side, and each one has dual 8GB dies. Add 'em up, and the drive has 256GB of flash memory onboard. Some of the NAND is dedicated to spare area and RAISE, dropping the 335 Series' advertised capacity to 240GB.

Our drive arrived in a retail kit that includes a 3.5" mounting bracket, SATA data and power cables, and a handful of screws. Intel provides free cloning software for folks looking to migrate an existing OS install to the SSD. It also offers an excellent SSD Toolbox application that's worth downloading regardless of whether you're cloning a current drive or starting from scratch.

Among other things, this utility can be used to secure-erase the drive and to update its firmware. It can also be configured to TRIM unused flash pages on a schedule, if you don't trust the drive and operating system to clean up after themselves. I particularly like the app's estimated life display, which is based on a SMART attribute that tracks flash wear. The SSD Toolbox can be used to monitor that and other SMART attributes, including ones that keep tabs on the total volume of reads and writes. According to the app, our test suite has hammered the drive with 3.5TB of reads and 2.5TB of writes.