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SanDisk Ultra Plus 256GB review

SanDisk Ultra Plus 256GB Review

Manufacturer: SanDisk
UK Price (as reviewed):
approx £138 (inc VAT)
US Price (as reviewed): $209.99 (ex Tax)

With the SandForce 2281 drive controller now nearing its second birthday, companies in the SSD market are beginning to develop different methods of improving drive performance, despite said controller having long been capable of saturating the SATA 6Gbps bus in sequential reads. Our SSD catch up article is well worth a read, as in it we pit four of the latest non-Sandforce drives against one another and the best of the last generation. Samsung's new SSD 840 Pro was particularly impressive performance wise, while the regular SSD 840 came out on top in terms of sheer value for money.

We've yet to look at a SanDisk SSD here at bit-tech, but it's hardly an unknown brand or small player when it comes to flash memory. It manufactures its own NAND in a joint venture with Toshiba and has a big presence in the OEM market and in consumer electronics shops. With us today is one of SanDisk's brand new Ultra Plus SSDs, and with a capacity of 256GB our sample is the highest end product of the range. It's not currently available in the UK, but our sources at PC Pro have informed us that it will retail for £138 on these shores, which places it directly in competition with Samsung's similarly priced SSD 840 250GB.

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Click to enlarge

SanDisk's two previous consumer SSDs, the Extreme and the Ultra, were both SandForce based, but the controller in the Ultra Plus range is now licensed from Marvel. Rather than a brand new controller, SanDisk has opted for a modified version of the 9174 controller as seen in drives like the Crucial M4 and Intel 510. The new controller is known as 88SS9175, or 9175 to its friends. The key difference between it and the 9174 is the increased power efficiency and a reduction in NAND channels from eight to four.

Each of the controller's four channels is paired with one of SanDisk's own 19nm based 64GB MLC NAND modules, which in theory should net it a performance boost in write speeds over Samsung's TLC based SSD 840 250GB. Indeed, its claimed maximum write speed is 445MB/sec compared to the Samsung's 250MB/sec. With a formatted capacity of 238.47GB, the Ultra Plus has a fairly standard 6.9 per cent over provision.

Like the NAND, the controller's firmware is produced in house by SanDisk, and as with the 9174 controller, the 9175 functions in tangent with a DRAM cache, specifically in this case a Samsung 128MB DDR2 800MHz package.
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Click to enlarge - the PCB inside the drive is tiny

The controller also utilises a technology dubbed nCache, whereby a portion of the MLC NAND runs in SLC mode such that data can only be stored in one of two states, rather than four, which improves write performance. The idea is that small file writes take place in the SLC portion of the NAND, with the benefit being that this temporary storage space is non-volatile, unlike the volatile DRAM. During idle times, it outputs these smaller writes in more complete chunks to the MLC portion, in theory keeping small random write performance up and write amplification over time to a minimum.

Physically, the drive is a 7mm high model and is therefore a suitable fit for notebooks where the low power consumption really matters. Our first impression upon picking it up was that it was very light, and opening it up reveals that this isn't just a consequence of the plastic casing as the actual PCB is less than half the size of its shell. A single thermal pad covers the drive controller, the DRAM cache and two NAND modules, with the other two NAND modules on the rear. It makes sense for SanDisk to utilise an existing and popular form factor, but the PCB's dimensions open up the possibility of a similar drive in a tinier package. Finally, just like the SSD 840, the Ultra Plus SSD comes with a three year warranty.

Specifications

Interface: SATA 6Gbps
Nominal capacity: 250GB
Formatted capacity: 238.47GB (6.9 per cent over provision)
Controller: Marvell 88SS9175
Cache: Samsung 128MB DDR2-800
Memory type/amount: 4 x SanDisk 64GB 19nm MLC NAND
Warranty: Three years