Flash Memory Offers Potential for Compact Storage Solution
By Bruce Schneier
November 16, 1992
While many types of removable media are good for long-term storage, they are often too bulky and expensive for compact devices such as printers, palm-size computers and network hardware.
That's why a growing number of vendors are swinging over to flash memory, also known as flash ROM, a form of nonvolatile memory that blends the rewrite flexibility of dynamic RAM with the permanence of ROM.
Though not a silver-bullet solution for all memory requirements, flash memory currently works well for storing a few megabytes of printer fonts, software or configuration data and has the potential to store much more.
"Any time you've got built-in code that's likely to change, flash ROM is an excellent solution," said Janet Woodworth, marketing communications manager at Intel Corp. of Folsom, Calif. "[With flash memory], code updates can be done remotely, on the fly, by end users," Woodworth said.
The BIOS code stored on motherboards of IBM PCs and compatibles is rapidly moving from permanent ROM to flash memory that can be updated. Apple won't comment on the implications for Macintosh CPUs.
The Big Flash
Most flash-memory designs evolved from EEPROMs (electrically erasable programmable ROMs), such as the chips that retain your laser printer's default settings when you turn it off.
Because of their greater capacity and efficiency, flash-memory chips are now used as solid-state "disks" for font storage in some PostScript printers. The Accel-a-Writer 8000 from Xante Corp. of Mobile, Ala., for example, comes with 512 Kbytes of flash memory and a 1-Mbyte flash-memory option.
"We found out that customers valued the fonts they already owned, not additional built-in fonts," said Xante President and founder Robert Ross. "They wanted to permanently download them but avoid the expense and complexity of connecting a hard drive to the printer; flash ROM seemed the best choice."
Xante refers to its Accel-a-Writer flash memory as a "virtual disk" since you can add and delete fonts to the flash memory as you would to an attached SCSI hard disk. Compaq Computer Corp.'s new Pagemarq network PostScript printers accept 1-Mbyte and 2-Mbyte flash-memory options for font storage.
Network routers run complex software that is updated periodically, so it's no surprise that compact, stand-alone products such as Compatible Systems Corp.'s AppleTalk-compatible Ether*Route routers use flash memory. According to the Boulder, Colo.-based company, both the Ether*Route and Ether*Route/TCP routers retain their operating software and network-configuration information in flash memory when the power is turned off.
Software updates can be permanently downloaded using Ether*Route management software. And Cayman Systems Inc.'s latest GatorBox CS now employs flash memory to store code.
Not for Everyone
While flash memory is useful, storage experts cite several reasons why vendors don't use it in place of dynamic RAM.
First, unlike RAM, flash memory must be erased before you can write to it, which takes time. Depending on the vendor, flash memory operates in the 55- to 120-nanosecond range, but erasure can take much longer - too long to function as nonvolatile RAM.
Furthermore, unlike DRAM, flash memory wears out after a number of erasures. Intel Corp. and Advanced Micro Devices Inc. guaranteed earlier flash-memory systems for 10,000 erasures; that figure has jumped to 100,000 erasures for their latest designs. That's plenty for occasionally updating stored system configurations, but it's a short life for application data, which may update hundreds of times per minute in RAM.
For solid-state disks, though, the new 100,000-erasure limit looks good. "One hundred thousand erasures amounts to 30 a day for 10 years," said Steve Grossman, director of operations for AMD's Nonvolatile Memory Division in Sunnyvale, Calif.
New flash-memory designs can instantly erase and reprogram specific sectors of memory - typically 16 Kbytes in size - rather than the entire chip, Grossman said, and good software can spread the erasure load evenly, thus making hard-disk-emulating flash-memory disks a distinct possibility.
"People can store their programs in flash ROM while updating data in DRAM," Grossman said. He added that flash-memory prices soon will match and surpass those of DRAM, since the flash-memory cell itself is easier to manufacture.
Louis Hebert, Flash Card product line manager at Intel Corp. of Folsom, Calif., said, "We envision half-gigabyte memory cards by the end of the decade."
Flash-memory vendors, at least, believe in flash memory's future. "Making higher capacities affordable is the primary thrust of solid-state storage," said John Reimer, vice president of marketing at SunDisk Inc. in Santa Clara, Calif. "We can make 100-Mbyte cards today, but they would be too expensive. In two years you'll see 40-Mbyte cards - maybe even 80-Mbyte cards - at a cost of $15 to $20 per megabyte."
Demand also may help drive down the price. Last year, according to AMD's Grossman, the total flash-memory market was only about $125 million. This year AMD foresees a $300 million market booming to more than $1 billion by 1995 or 1996.
The new flash-memory standard endorsed by Apple, called PCMCIA-ATA (Personal Computer Memory Card International Association-AT Attach), will help make credit card-size flash-memory modules very attractive storage devices. The standard will help ensure that cards can be moved from one system to another.
"You'll be able to take the same memory card from your Newton to your HP 95LX to an airport kiosk," Reimer said. "The technology will be in the card; the CPU won't have to manage the flash memory."
Photo of Bruce Schneier by Per Ervland.
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