Solid state disks and flash modules for (low spec) notebooks

Flash memory device specialist SanDisk has announced flash modules with 4, 8 and 16 GB especially for low-end netbooks, a wide range of which is expected to be presented at Computex. These small storage units called pSSD (parallel ATA Solid State Drive) are scheduled to reach the market in August. Communication between the SSDs and the computer is via IDE by means of a 40pin ZIF (Zero Insertion Force) plug. According to the datasheet – PDF file –, they reach a maximum sequential transfer rate of 39 MB/s when reading and 17 MB/s when writing, although in practice transfer rates are often limited by the system the SSD is plugged in to.

Intel is also expected to present similar modules at Computex. It's probable Intel will show their quite small Z-P230 PATA Solid-State Drives – PDF file – measuring 54 mm × 38 mm × 4 mm at the exhibition. Like the SanDisk modules they also communicate via IDE over a ZIF plug and consume very little power. In its datasheet, Intel speaks of 1.65 milliwatts when idle and 314 milliwatts when reading or writing. Initially, 4 and 8 GB versions are planned, both of which will probably use only MLC flash. A 16 GB version is expected in the fourth quarter. It is likely to be rather slower than SanDisk's pSSD at 35 MB/s reading and only 7 MB/s writing. So far neither manufacturer has released prices on these products.

SuperTalent will be presenting fast 1.8" SSDs for ultra-mobile PCs (UMPCs) at Computex. The models called MasterDrive KX have either 30, 60 or 120 GB and also use MLC flash. They make contact with the host via a slender micro-SATA interface (1.5 GB/s). The maximum transfer rates are expected to be 120 MB/s for reading and 40 MB/s for writing. SuperTalent recommends a relatively low sales price of $679 for its top model with 120 GB. The other two models are expected to cost $449 for 60 GB and $299 for the 30 GB.

While TDK will not itself be at Computex, it has also presented new 1.8" micro-SATA SSDs, though they implement the more expensive SLC flash. The models in the HS1 series are available with 16, 32 and 64 GB at a price of $900, $1500, and $2000, respectively. The discs transfer data at a maximum of 100 MB/s when reading and 50 MB/s when writing; the data are stored with 128-bit AES encryption.

pSSDs use either the older Single Layer Cell (SLC) or Multi Layer Cell (MLC) flash memory chips. MLC chips offer double the capacity at lower cost than SLC, but memory cycle times are slower and the maximum rated number of cycles before failure is much lower. For example flash chip manufacturers often quote 10,000 cycles for MLC compared to 100,000 for SLC. Frequently, this information does not appear in the marketing specifications for finished flash products and flash memory product manufacturers are extremely coy about quoting lifetimes for their products, or revealing which chip types they use to build them.

Manufacturers of conventional hard drives apparently still do not think competition from solid-state disks poses much of a threat in the near future. Nonetheless, Seagate plans to start selling its own flash disks soon. The first models, which will mainly be intended for corporate use, could hit the market next year. Seagate's CEO Bill Watkins has been quoted in US media saying that his company will look into consumer SSDs when the price drops to 10 cents – or roughly 5p – per gigabyte. Current UK hard disk prices are around 20p per GB and 500p per GB for flash.

iSuppli analyst Krishna Chander believes that solid-state disks will catch up with conventional hard drives over the next three to five years in terms of price per gigabyte and reliability. Although price is certainly an issue, fears over flash reliability, due to the limits on the number of write / read cycles for individual flash cells, are exaggerated. In practice, in most applications, even current flash devices may be used for 5 to 10 years before the specified maximum cycle limit is approached. The Mean Time Between Failure (MTBF) ratings for magnetic hard disks provide no greater assurance of data safety.

Manufacturers like Seagate or their main competitor Western Digital, with a core business in hard disk manufacture, will need to consider very carefully how they enter the solid state disk market or risk obsolescence.

(trk)