Original URL: http://www.theregister.co.uk/2010/08/20/sandisk_issd/

SanDisk bigs up its flash postage stamp

Just keep taking the tablets

By Chris Mellor

Posted in Storage, 20th August 2010 08:19 GMT

SanDisk has announced a postage stamp-sized flash iSSD product for tablet computers at the Flash Memory Summit, with capacity ranging from 4GB to 64GB.

IDC has conveniently defined a new flash product category, embedded flash, for what are called "highly portable consumer electronics devices", presumably meaning anything from music players through mobile phones to tablet computers. SanDisk says the iSSD is the first product in this new category, which IDC seems to have defined so as to rule out all flash products shipped in mobile phones, music players and tablet computers to date. Frankly, that seems idiotic.

Jeff Janukowicz, IDC's research manager for solid state drives, is quoted in the SanDisk release talking about: "The ultra-thin tablet and mobile computer markets" and "stringent size requirements of small and light devices". Even if we grant him that ultra-thin tablets are a proper computing category compared to thin tablets and, logically, thick tablets, and that mobile phones which, denying common sense, must be supposed not to use embedded flash, the distinction between this and non-embedded flash used in all the other mobile internet devices to date seems artificial.

Some observers may think dark thoughts about IDC inventing a market category to suit SanDisk but we couldn't possibly comment on that notion.

Maybe the category's real distinction is that it refers to BGA-packaged flash? Samsung's OneNAND (pdf) flash came in a BGA package so if BGA-ness is the defining factor then Samsung got there before SanDisk.

The iSSD product is 1.85mm thick and claimed to be smaller than a postage stamp. We're all so blasé about physical size that we're not that impressed - SanDisk announced a finger nail-sized SSD only last month. That one went up to 16GB of capacity but the iSSD holds four times more data. The iSSD uses multi-level cell (MLC) flash, probably two-bit, and if it is used in devices that are used more for content consumption than content creation the well-known MLC write endurance problem should be much less of an issue.

The other measurements are 16mm x 20mm and the little tab weighs less than a gram if it's a 4GB jobby and a little more if it's a 64GB version. It comes with a SATA interface (SATA II we reckon) in a Ball Grid Array (BGA) package (157 ball BGA with 0.5 mm pitch). It offers 160MB/sec sequential read and 100MB/sec sequential write speeds.

SanDisk says the packaging means manufacturers can "avoid the additional weight and thickness required by a connector-based SSD solution". It also means that the SSD sits snugly against its host board and impedes any cooling airflow less - which only really matters if it is used in a device with a fan, such as a notebook computer.

It supports SMART diagnostics and the TRIM command and its write endurance is defined by SanDisk as the total number of terabytes that can be written (TBW) before the drive fails. For a 4GB model it is 2.5TB, 5TB for the 8GB version, and so on linearly to 40TB written for the 64GB version. The predicted lifespan requires customers to know the average data write rate per time period and this is used to divide the TBW figure and so produce a working life period.

The iSSD, available for sampling now, is being evaluated by some unidentified manufacturers and its price will vary with the order quantity. ®