Hard Disks and Flash Memory Square Off In Pen Market

Flash has many advantages but much higher cost

With power consumption, rugged design, and size being at a premium in pen-based systems, the two main technologies competing for mass storage slots are flash memory devices and miniaturized hard disks. Before comparing the two technologies, we review some of the recent product announcements.

Several manufacturers have recently announced low power 1.8 inch hard disks with storage capacities as high as 85 MBytes. Aura Associates has introduced a 1.8 inch 85 Mbyte hard disk, which will reportedly also be marketed by NEC. The drive uses the standard IDE AT interface. Pricing has not been announced. Ministor Peripherals is offering a 64 Mbyte 1.8 inch drive with a PCMCIA connector (however, a special slot is required since the dimensions of the drive are larger than the standard PCMCIA slot). Ministor’s VP of Marketing, Jim Miller, says that the 32 and 64 Mbyte models will ship to OEMs in the next few months priced at about $6.00 per megabyte, with prices dropping to $4 per megabyte by next year. Both the Aura and Ministor drives measure about 50x70x13 mm and weigh less than 100 grams.

In the flash memory arena, SunDisk Corp. has the inside track for flash memory mass storage systems. Several manufacturers, including Grid and IBM, have announced that they will use SunDisk’s solid state memory devices with capacities ranging from 2.5 to 40 Mbytes. SunDisk’s SDI Series mass storage systems use the IDE AT interface although the company plans to support the PCMCIA interface in future products. According to SunDisk’s John Leibowitz, PCMCIA has recently agreed upon an extension to the current standard to include a standard protocol for connecting drives and storage devices with the IDE AT interface. SunDisk’s flash storage devices will cost at least $50 per megabyte.

In other flash memory news, Advanced Micro Devices has begun sampling a new single voltage flash memory chip, the AM29F010, which doesn’t require a second 12-volt power source for writes. AMD’s announcement of the AM29F010 suggests that system design can be simpler because a second power source isn’t needed. The chip may also improve computer performance because memory writes won’t use as much power as with other flash memory components; AMD says that the new chip uses only one-third as much power for writing as dual-voltage flash memories. AMD says that the 45 nanosecond, 1 Mbit chip will be available in quantity within the next few months; pricing is unannounced. Both 4- and 16 Mbit versions are under development.

Intel has announced a 8M-bit flash memory chip and a $600 flash memory card that can use up to 20 of the 8 Mbit chips. This translates to a 20 Mbyte memory card at half the price of current Intel offerings (the company has been selling a 4 Mbyte card for about $1200). At the same time, Intel announced that the company will join forces with Microsoft to develop a new version of the Flash File System to support the new Intel card.

How They Stack Up

In all technical aspects, flash memory devices offer significant advantages over hard disks. They are smaller and lighter (SunDisk’s SDI devices are about one half the thickness of 1.8 inch drives and weigh about half as much). Flash memory uses much less power. SunDisk draws 100 milliamps (mA) while reading and 200 mA for read/write, while the hard disks discussed here draw at least 500 mA for the same operation. Flash memory devices can power up from sleep mode much faster than hard disks, thereby saving additional power. Flash memory devices offer much faster performance than hard disks, having zero seek and latency times (according to a PC Week benchmark cited in SunDisk’s press release, SunDisk is 75% faster than hard disks). And, perhaps most importantly, flash memory devices are more rugged than hard disks. SunDisk claims up to 500 G’s of operating shock versus 10 to 20 G’s for the hard disks. Ruggedness will be a major consideration for mobile computing.

The Drawback is Cost

But in spite of all these advantages, flash memory has one glaring disadvantage and that is cost. Currently, flash memory storage costs about 10 times as much per megabyte as hard disk storage. And that price comparison is on the basis of Intel recently dropping the price of its flash memory chips. While SunDisk claims that its SDI Series will sell for about $50 per Mbyte, the current price for evaluation units ranges from $150 to $250 per Mbyte depending on the storage capacity (the higher capacity devices are cheaper).

Another issue with flash memory is reliability during extended usage (endurance). Traditionally, flash memory has been used to store system level programs which are rarely modified (e.g. system or graphics BIOS), therefore requiring very few write operations. In the mass storage environment, however, the flash memory device must be able to withstand hundreds of thousands of read/write operations. SunDisk claims their devices can handle over 1 million read/write cycles. Nevertheless, endurance is a much more technically challenging problem for flash memory than it is for hard disks. This contributes to the high cost of flash memory.

The Bottom Line

The bottom line is that both flash memory and hard disks will be used in pen-based systems. In the near future, systems with flash memory storage will be a lot more expensive than systems using hard disks. But as volume increases, the price for flash memory devices will drop significantly. Nevertheless, this process could take several years. The decisive factor will be power consumption and environmental conditions in which the system will be used. If the system is going to get banged around and dropped a lot, it may be worth the expense to go with flash memory storage. If the machine will used in an office environment and can be recharged more frequently, hard disks will offer a more economical solution for some time to come.

Contact:
Advanced Micro Devices 408-732-2400, Aura Associates 408-252-2872, MiniStor Peripherals 408-943-0165, SunDisk 408-562-0500