Cost reallocation, reduction put new spin on rotating storage

Pundits have long pontificated on when and if the price-per-bit of semiconductor memory will cross under the magnetic-storage cost curve. Looking at the situation from one perspective, magnetic storage is winning the tug of war by a large margin. Bargain shopping quickly unearths 100-Gbyte hard drives for much less than $100, and magnetic tape is even less expensive. DRAM and flash memory aren't selling for anything near $1 per gigabyte and won't be for a long time to come. If you view the situation from a different angle, however, semiconductor memory has seemingly won out. It's nearly impossible nowadays to find a 1-Gbyte hard-disk drive, except perhaps in a surplus store; flash-memory cards have taken over that business.

The answer to the "which-is-cheaper" question depends on the end application and its required density and on other factors, such as performance, power consumption, and ruggedness. If the systems you design need lots of storage capacity, and price is your paramount concern, hard drives will likely win the fight. When storage requirements plateau, though, or when factors other than price come to the forefront, hard drives' downsides become more apparent, and the battle turns in semiconductor memory's favor. Cornice's Storage Element, roughly the same size and thickness as a CompactFlash card, finds itself between these application extremes (Picture). The 1.5-Gbyte device's density encroaches on the high end of flash memory's territory, which Toshiba's (www.toshiba.com) recently announced, 2-Gbit, single-level-cell flash memory reminds us, is ever-expanding.

The Storage Element's $65 (100,000) price may at first seem attractive. Consider, though, that less-than-$160, 1-Gbyte CompactFlash cards are now flooding retail channels. Subtract the retail-margin markup, along with the cost of the memory controller, card housing, and other overhead, and you get a raw flash-memory price of less than $100. Cornice's executive team has an extensive background working for various hard-disk-drive manufacturers, so it's not too surprising that the Storage Element builds on a hard-drive-like foundation, including servo and preamp ICs. Cornice moved the mass-storage controller into a separate 200,000-gate, $4 (100,000) Transition IC, which, as its name implies, Cornice views as an interim step to your ultimate integration of the required logic circuits, along with 48k words of firmware and 40 kbytes of rate-matching FIFO memory, into your system ASIC. Toward that end, the company plans to provide royalty-free Verilog code detailing the Transition IC's functions. The Storage Element's minimum sustained-transfer rate for a continuous file and single track is 4 Mbytes/sec; its minimum continuous-file, multitrack counterpart is 2.7 Mbytes/sec.

Cornice representatives are careful to point out that the product is not simply a shrunken hard drive. The company did not design the device for multithreading or multitasking, and it does not support PC-like buffering and elaborate caching, all features that company officials believe are relatively unimportant in Cornice's target markets: digital-audio players, PDAs, digital-still cameras, videocameras, and the like. A 20-conductor bus interconnects the Storage Element and Transition IC, and the Transition IC communicates with the rest of the system over, according to Cornice, a bus that is "similar to a CompactFlash True IDE Mode interface." Development partner Texas Instruments (www.ti.com) plans to build the 20-conductor Storage Element bus directly into future generations of its DSPs and system CPUs. Cornice plans to begin shipping 2-Gbyte Storage Elements by year-end, and, assuming that the technology's success leads to high volumes and consequent cost efficiencies, the company believes it will be able to sell Storage Elements for less than $50 by the middle of the decade.

Typical current draw for the 3.3V Transition IC in read, write, sleep, and nonoperational modes is, respectively, 90 mA, 90 mA, 5 mA, and 100 µA. The 3.3V Storage Element will survive a 1m drop, and 1.5m-drop tolerance is on the way. In spin-up, read, write, idle, and nonoperational modes, its typical current draw is, respectively, 207 mA, 226 mA, 235 mA, 30 mA, and zero. Company literature states that you can achieve the "lowest power consumption when the host system maximizes the time that the Storage Element and the Transition IC are in the nonoperational mode...when the host-system RAM can buffer enough data and cache the file-system data structures to minimize accesses to the Storage Element and Transition IC." Assess the likelihood that your software's access patterns will enable you to power down the Storage Element during a high percentage of total system uptime. Also assess the cost and power consumption of the required buffer memory and the 1.5-sec maximum Storage Element delay from power-off to ready when comparing the overall viability of Cornice's product with that of alternative mass-storage technologies.

Cornice, 1-303-651-7291, www.corniceco.com.