steve667,
Steve Lee is right about the 100,000 write cycles of Flash -- it's not a lot, but it's enough for "occassionally accessed" storage, which is very different from the hi-frequency use of "memory".
Note also, that the controller in Sandisk cards use a spare-out function to replace those sectors that have been used almost to their limit, with fresh, "spare" sectors. This makes it so the lifetime of the card is not limited to the lifetime of the most frequently accessed sectors, and greatly extends usable lifetime of the card.
There was a very good article, which I just came across, in the April issue of Wired magazine with an interview of Stuart Parkin, IBM's MRAM guy, and a review of the leading edge of magnetic memory development throughout the industry. Bottom line, is that commercial products are 5 years away, especially in the hi-density area. I think OUM is much closer than that, however, since Intel/Ovonyx is working now on a 16Mbit sample chip. No time-table has been offered, though.
Here's some excerpts from the Wired article:
wired.com
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Over the next five years, further iterations of Parkin's MRAM chips will become increasingly smaller and able to hold more data. But with each successive prototype, a range of microfabrication obstacles must be resolved. And IBM will also have to hammer out the best methods for mass production. After that, MRAM chips could be available to consumers at a cost comparable to DRAM, since MRAM doesn't need all the supporting circuitry to connect with a power source. But because it cuts out the delays associated with transferring electricity between the power source and the chip, MRAM would be up to 30 times faster.
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A more direct threat to IBM's instant-on, no-boot chip is the MRAM work under way at Honeywell. "MRAM is perfect to fill the need for nonvolatile memory," says Theodore Zhu, head of Honeywell's MRAM technology group. His company has produced larger magnetoresistant chips with 16 Kbytes of memory for various military apps (MRAM can survive radiation exposure). But Honeywell broke its promise to unveil a 1-Mbit chip by the end of 1999, which would have put the company far ahead of IBM. Perhaps that's because Honeywell's primary customer is the military, says Parkin, "so they tend to build devices that wouldn't be commercially viable."
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Another contender in the MRAMrace is the US Naval Research Laboratory in Washington, DC. "We've arranged magnetic material in tiny rings - like washers stacked on top of each other," says NRL physicist Gary Prinz. "You can run a wire right down the middle and switch the direction of the magnetic field in the rings." Prinz claims his design overcomes many of the roadblocks other MRAM structures encounter, such as high electrical resistance and imprecise control of magnetic switching.
The NRL work is impressive from a fabrication standpoint, says Parkin, "but it doesn't seem to have commercial potential. The electrical resistance is too low, and without some resistance, you don't get a signal."
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While Parkin and his five-member development team perfect their new chips, Saied Tehrani, chief researcher for Motorola's MRAM project, says he's working on a similar, but not necessarily competing, technology. "We're not a stand-alone memory company and don't plan to compete with the DRAM makers," he notes. Instead, Motorola is steering away from the instant-on computer idea and looking at ways to integrate logic and memory MRAM chips for embedded systems in portable communications devices. "We see MRAM as a universal memory, with the positive attributes of technologies like flash and static RAM," says Tehrani, "and we anticipate a rollout of some kind in about five years."
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Every year since 1994, IBM has topped the US Patent and Trademark Office's annual tally of new patents - 2,756 in 1999 - and the company has spent more than $5 billion on R&D every year for the last decade. For Parkin, this means almost limitless resources for pursuing the instant-on computer.
While IBM VP and director of research Paul Horn won't reveal how much Big Blue has earmarked for the MRAM project, a clue can be found in Parkin's machine shop, packed with multimillion-dollar, one-of-a-kind tools for producing new experimental sandwiches. In one area, he shows off his newest toy, a $1 million, computer-controlled vacuum chamber capable of cranking out preliminary MRAM materials even faster than his prototype sputtering chamber. When we return to his lab, Parkin softly quizzes a colleague, then bustles over to a computer near the old sputtering machine, where a data curve from a new compound is appearing onscreen. "I can't tell you about this one yet," he says, gesturing to the plot, "but it looks very good."
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