Intel: Non-volatile memory shift means chips need an overhaul

Processor architectures and filing systems will need dramatic redesigns to take advantage of upcoming non-volatile memory technologies, Intel has said.
Written by Jack Clark, Contributor

Current processor and filing system designs must be revamped to get the most out of non-volatile memory technologies, Intel has said.

Though we are still a few years away from seeing a replacement for flash that will dominate the market, when it does chipmakers and filing system designers will need to alter their technologies to take advantage of the low latencies afforded by this new class of memory, Intel's chief technology officer, Justin Rattner, told ZDNet on Tuesday at the Intel Developer Forum in San Francisco.

"I'm reasonably confident that... non-volatile technologies will replace flash and bring non-volatile memory very close [to compute] with dramatic improvements in latency," he said. "Architectures will clearly have to react and respond to that."

Memory hierarchy

The jury is still out on exactly which technology will come to replace flash. It could be any one of phase change memory (which is currently being developed by IBM), memristors, which are being worked on by HP and Hynix, or spin-transfer torque, Rattner said.

Non-volatile memory can retain information without power — unlike RAM — and has fast access times, providing both huge power savings and the potential for much faster data transfer.

"Within probably the next three, four or five years we're going to have that memory, and we need to start now to look at the operating system issues and file system issues to take advantage of it," Rattner said.

When you change the memory hierarchy, it has huge knock-on effects on how computation works, he explained.

"Through most of the history of computing, we've assumed a persistent storage system — including the file system and virtual memory system — based on the characteristics of moving-head disks — devices with a very high access latency organised into fixed-sized blocks of thousands of bytes," Hank Levy, a professor of computer science and engineering at the University of Washington and non-volatile memory chip design researcher, told ZDNet on Thursday.

"These characteristics run very deep at every level of the software stack. These new memory technologies are fundamentally different both in their low access time and their fine-grained (byte-level) access."

If chip and filing system designers do not make fundamental changes to take advantage of new memory, "then we'll be missing an opportunity to really benefit from what these technologies can provide", Levy said.

Intel Labs research

To that end, Intel Labs is currently doing research about the implications of what happens when main memory becomes non-volatile, Rattner said.

"These new memory technologies are fundamentally different both in their low access time and their fine-grained (byte-level) access" — Hank Levy

"Right now all extant architectures assume all [directly CPU-accessible] memory is volatile," he said, noting that Intel is looking at adding instructions to processors to help them correctly move data between cache and into persistent memory and back.

Along with processors, Intel is thinking about filing systems as well as it would be "ridiculous" to use conventional techniques on top of non-volatile memory.

"Those [filing systems] are all optimised for when access times are in the tens of milliseconds, but [with non-volatile] now they're in the tens of nanoseconds.," Rattner said.

Ultimately, architectures will have to change because widespread use of non-volatile memory will make the "distinction between main memory and bulk memory... begin to disappear", he added.

Race to replace flash

Richard Coulson, director of the storage technologies group within Intel's technology and manufacturing group, pointed out that there is currently "a race" between spin-transfer torque, memristors and PCM to see which technology can be mass manufactured at a low enough price to be viable.

"We don't know which one of those or others will ultimately be cost effective," he told ZDNet on Wednesday. But when one of these comes in, "it changes the whole memory storage hierarchy".

Unfortunately, a lot of further development work depends on which non-volatile technology comes to dominate, and that is as yet unknown. "The base memory technology is the biggest wild card at the moment," Coulson said.

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