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InterphaseTECHNOLOGY IN CONTEXT
Embedded Memory System Options
Phase Change Memory will Change Memory System Design
Dramatic changes are coming to the way nonvolatile and volatile memories are used, and with these changes firmware will evolve to take advantage of the new memory topology, making systems less complex, more reliable and lower in cost.
JIM HANDY, OBJECTIVE ANALYSIS
Phase Change Memory or PCM is a new memory technology being explored by several companies. This technology fits between today’s volatile and nonvolatile memory technologies to provide features that appeal to system designers who have had to work around the idiosyncrasies of existing memory technologies for the last several years.
PCM is simple enough to use so designers can begin to forget all the strange work-arounds they must use now to design NOR or NAND flash into their systems. PCM also helps realize some significant improvements in time-to-market as well as related improvements in performance, cost and code density. In certain cases, designers will find it worthwhile to rework existing designs to convert them from flash to PCM. Many designs should also be able to reduce or even eliminate a RAM chip that was once required to compensate for flash’s slow and messy programming protocol.
To help illustrate the strengths and weaknesses of today’s dominant memory technologies against PCM, Table 1 presents the performance of seven key metrics for each of three technologies: DRAM, NAND flash and phase change memory (PCM). Relative performance for each technology is given for sequential and random read and write, power consumption, volatility and cost per bit.
Why PCM? Why Now?
Why is PCM interesting and why is it now reaching production? There are several reasons for both. The biggest reason that PCM has been unable to make its mark in the market today is that existing memories have proven to be far more economical than any new alternatives. This has been the case for quite a long time, shutting any newcomers out of the market. On any given process, these alternative memories have either suffered from having a larger die size than their entrenched competition, or the wafer processing costs have been significantly higher. Cost is everything in the memory market, so any chip with a higher manufacturing cost doesn’t stand a chance of displacing any existing technology. This will change soon, as PCM costs close the gap with DRAM over the next few years.
On the positive side, there are a few reasons why PCM has recently become attractive. For one, materials have progressed significantly over the past decade and it is now much more feasible to produce the high-purity thin films that are required by the phase change material. Also, there have been numerous breakthroughs with the chalcogenide materials used in PCM because they have been used in high volume to manufacture both CD-R and CD-RW disks. Along with this has been a vast increase in the understanding of the physics of these materials. Process shrinks have played their part: In the past, the amount of material to be heated was relatively large, requiring significant energy to achieve a phase change. As processes have shrunk, what once seemed like an ocean of material to heat has now plummeted to something more akin to a bathtub. Finally, a general acknowledgement that flash memory will soon reach its scaling limit has added impetus to develop follow-on technologies that will continue to scale past this limit. Although flash’s scaling limit has been postponed for a number of years, all flash makers agree that there will soon come a time when flash can no longer be shrunk to the next process node and the industry will have to change technologies.
Figure 1 illustrates the phenomenon behind this scaling limit: the number of electrons stored in a flash bit is on a steady decline. The graph indicates that both NAND and NOR flash could store fewer than 10 electrons per bit before either of these technologies reaches the 10nm process node in about eight years. Ten electrons is far too few to store multiple bits in MLC in a noisy environment, so the minimum required number of electrons is significantly higher than 10, closer to 100 per bit. Even at this level the low number of electrons makes it difficult to meet the reliability requirements of existing applications.
Figure 1
In both NAND and NOR flash, the electrons per bit are rapidly declining with reduction in process geometry to the point of unreliability.
Phase Change Memory is already available. Samsung announced a PRAM prototype in 2004 that is a precursor to impending production. Shortly afterward Numonyx announced a prototype PCM device that started shipping in limited production toward the end of 2008. One other company—BAE Systems—has been shipping its C-RAM chips into the aerospace market since 2006. This market is interested in PCM since it is immune to bit errors caused by alpha particle radiation.
Discuss
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Mr. Handy originally wrote this horrendous piece of "objective analysis" in August of 2009, and he should be ashamed for misleading his clients and the innocent readers about the true state of phase-change memory. The "report" starts with the lie that "PCM is a new memory technology, " while in fact the technology dates back to 1960s, and Intel's co-founder Gordon Moore, the author of Moore's Law, co-authored an article about it in 1970. The lies get progressively worse. For example, the author claims that "PCM is simple enough to use," but fails to mention the high-temperature instability and the lose-data-in-reflow issue, the poor density, and high power consumption and very low speed in write, etc. He is also lying that "Phase Change Memory is already available." The fact is, no vendor offers this memory commercially today: not Numonyx, who did indeed claim they shipped product commercially in 2008, but recently admitted that the product is not really commercial; not Samsung, who don't even have a phase-change product category on their web site; not BAE, who implied commercialization in 2006, but must have failed their Q- and QML-V level military qualifications again (originally planned for 2006, and then again scheduled for the Fall of 2009 and early this year, respectively). No product on the market today uses phase-change memory. Period. Now, let's address the delusions of the previous commenter (DAD) addressed to "randy:" ECD does not not receive any royalty from phase-change memory, as phase-change memory is not commercial. It is Tyler Lowrey, not Tylor Lawrey. Beceem is not a Ovonyx licensee. The override is 0.5% of Ovonyx’ annual gross revenue, not 1%, and the Ovonyx royalty percentage has not been disclosed (but was indeed 3% when Micron signed the exclusive royalty-bearing agreement for phase-change memory with ECD in 1994). Intel has no interest in using PCM in processing chips, as they know that PCM is slow and unstable. Micron announced their intention to acquire Numonyx in 2010 (not in 2009) and the deal has not closed yet. Micron, as mentioned above, did not need Numonyx to acquire a phase-change memory license - they had already done so in 1994, 6 years before Numonyx (then Intel) got their license, and in 2004 officially declared that PCM does not scale. Samsung is not doing anything serious with phase-change memory at this point (they haven't even published a datasheet). Intel has not released any phase-change processing chips and has absolutely no plans to do anything like that. |
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Wednesday April 7,2010 Hi randy, Here is an Article about Phase-Change Chip technology. While it is well presented, it is mostly just a rewrite of previous publications. Dates and time of development and commercalization are that of the writer, for no one knows for sure when this will take place. Here is my opponion on this,,,, As you know, ECD holds the basic patents and receives a royality on its use. Presently, it is very small for the only commercalization to-date comes only from CD-RW Computer Disc. While ECD has turned over this technology to OVONYX, their joint venture with Tylor Lawrey and Intel,which has licenced several outside firms including Samsung, Numonyx, BAE Systems, Beceem and others by retaining a 3% royality,plus a 1% override to ECD. Intel became a late partner in Numonyx (10% interest) by agreeing to fund 100% of its cost. Their interest being in Computer POCESSING CHIPS because they are not into MEMORY CHIPS. Intel then formed NUMONYX, a partnership with S G Microneletron A G in Europe to develop Phase-Change MEMORY Chips. In late 2009, Numonyx was baught out by MICRON Technology through issueing shares to the partnership. NOW, Intel is taking a more agressive managment in Micron. who obtained phase-change royality rights that Numonyx held. NOW,,,,, IMHO, Samsung is going full boar with Phase-Change in both Processing and Memory chips with Bata chips allready produced, while Intel also has released bata Processing Chips and now, Micron, being only in Memory chip are furthering Numonyxs Phase=Change development. IN THE END,,,,, i think SAMSUNG will be the first out with P-RAM, for Intel is laying back not wanting to be sited once again with lawsuits for a monopoly in the industry. Intel, from the very beginning, has directed everything that has taken place since aquiring an interest in OVONYX that is only a P-Ram research firm that will never produce chips, only sell the royality rights to others for production. regards, DAD P.S. Truste the Link works, please advise |