Flash may be getting all the attention, but the boffins are working hard to ensure we have options to flash. We need those options because flash has some serious limitations, like random write performance and density, that we may not be able to overcome.
On the other hand it is easy to underestimate the power of sustained investment in R&D. Disk drives have successfully fended off numerous would-be usurpers thanks to their incredible areal density growth.
Now flash is facing a challenger
Intel and STMicroelectronics’ new phase-change memory threatens flash, but not any time soon. Unveiled at ISSCC, the thermal phase-change device can store 2 bits per cell, like MLC flash.
I asked Jim Handy, of Objective Analysis, a semi-conductor market research firm, for his take on the Intel-STM announcement. He responded:
The big question is “When does Phase Change stand a chance?” I doubt that it could be competitive today because a wafer with a new material is bound to be much more costly than a pure silicon wafer until volumes get up, and the volume won’t get up until the price is competitive with flash. The number of chips per wafer is about the same for PCM as for NOR flash, so there’s no cost advantage from die size.
Once flash reaches its scaling limit brick wall (which was expected to be 2006 at 65nm, then at 25nm in 2012, now looking like 10nm around 2016) then PCM will zip right past it. Trouble is – that brick wall has legs and keeps zipping ahead of us.
Until then PCM should have trouble competing on cost, and cost is everything in the semiconductor memory markets.
One advantage PCM has is that it has a fast write, so in many cases a PCM chip can replace a flash and a RAM. This means that the cost target is something higher than simply matching a NOR price.
The significance of an MLC PCM is that it puts PCM on the same footing as MLC NOR. Had that not happened, then there would have been a longer delay before PCM replaced NOR, since a PCM die size would have been twice as large as an MLC NOR of the same density on the same process.
As for PCM replacing NAND, wellllll…… that’ll take longer since NAND’s about 1/3 the cost of NOR. The same brick wall impacts both technologies, though, so it will happen!
Thanks, Jim. I hadn’t realized that PCM could replace a NOR and a RAM chip.
The StorageMojo take
Jim’s take is better informed than mine. My take away is that the growth of PCM will depend on how broad a market niche it can build for itself over time. That won’t be easy.
Comments welcome, of course.
And for the record, STEC has already mitigated the random write concerns you describe at the drive level, and there undoubtedly will be other vendors in this space.
Meanwhile, cached storage arrays (DMX, USP, etc.) have long hidden the slowness of disk drives by buffering writes, and this same technology also hides the inherent write slowness of raw (unbuffered) flash.
There is no need to wait for PCM to have cost-effective solid-state storage – in the right platform and/or with the right drives, you can take advantage of the benefits of solid-state storage with today’s NAND devices.