Flash drives ready to jump in capacity

In the wake of a series of technical announcements from flash memory supplier SanDisk, larger-capacity solid-state drives are on the way.

Flash memory is gaining as a replacement for hard drives in ultra-thin, ultra-small notebooks such as the MacBook Air and Asus Eee PC. Why? Flash uses less power, generates less heat, and has faster access times than hard drives. The Air, for example, offers a 64GB flash-based SSD as an option while the Eee PC is sold standard with flash storage.

There is a big catch, though. High-capacity SSDs are expensive. Prohibitively so. The flash drive in the pricier $3,098 Air is the main culprit in the gaping $1,300 price difference with the lower-cost hard-drive model ($1,799).

Update: Historically, flash memory has had limited write cycles. That is, flash can eventually "wear out" after hundreds of thousands of write cycles--though firmware that spreads the writes over different sectors can extend the write cycles. It remains to be seen if this is an issue with SSDs used in the newest notebooks such as the Air.

The low power and high speed, however, make a flash drive almost irresistible for some users. A SanDisk SSD 1.8-inch drive achieves a sustained read rate of 66MB/sec and a random read rate of over 7,000 inputs/outputs per second for a 512-byte transfer, many times the speed of a hard drive--which must move an arm across a spinning platter to find data, the so-called seek time of a hard drive.

SanDisk will not discuss future pricing but as larger-capacity SSDs hit the market, prices are certain to fall. And eventually these will be steep price drops. For example, an 8GB SanDisk flash card now sells for about $80 at resellers. A few years ago consumers would have paid this much (or more) for a 1GB drive. (And a 1GB card was originally priced at $500 in 2004!)

SanDisk and Toshiba will start making flash memory on a new 43-nanometer manufacturing process that will result in SSDs later this year with capacities that should approach those of today's mainstream 2.5-inch hard drives, ranging between 120GB and 160GB.

The two companies recently achieved 32-gigabit (Gb) density, according to Khandker N. Quader, SanDisk's senior vice president of flash memory design and product development. The 32Gb die combined with multilevel cell (MLC) technology--which uses multiple levels per cell to allow more bits to be stored--"doubles the SSD capacity points," Quader said in a written response to questions.

Flash based on "X3" technology is another new development, Quader said. "This is an important milestone (and) allows us to do 3bits/cell as opposed to 2bits/cell thereby providing improved manufacturing efficiency," he said. "So a combination of technology scaling (i.e., 56nm to 43nm) and the bit scaling (i.e. 2bits/cell to 3bits/cell) is extremely powerful for manufacturing efficiency and for increasing capacities of flash memories."

But there are challenges. Moving to X3 can affect performance. "One very important point to take into consideration is that X3 is not a simple memory to manage," Quader said. "This is the first generation X3. We expect this to evolve in 2008."

SanDisk has also developed a 43nm 16Gb MLC for MicroSD, according to Quader. MicroSD is a tiny flash chip used in mobile phones. The new technology will double the capacity of current 8GB MicroSD, he said.