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3D Xpoint memory: Faster-than-flash storage unveiled

bbc.com

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Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#41

Post by david-given »

adsr wrote: post #16

I hope someone will give a push behind MRAM which seems like a more interesting option imo. MRAM has similar performance to SRAM, similar density to DRAM but much lower power consumption than DRAM, and is much faster and suffers no degradation over time in comparison to flash memory. It is this combination of features that some suggest makes it the “universal memory”, able to replace SRAM, DRAM, EEPROM, and flash. ht…

There's also FRAM, which has also been around for a while? I have an MSP430 microcontroller where the primary storage is 64kB of FRAM. It's great; performs like SRAM, but is totally persistent, and doesn't wear out.

The largest devices I've seen are 4Mb (512kB), which isn't a lot by PC standards, but is dead handy for embedded.

browses

Oho, they make one which is pin-compatible with SRAM chips!

http://www.fujitsu.com/global/products/devices/semiconductor...

Price looks like $15 a single part to $12 for ten. Ouch. If we assume that it's about $20 a megabyte in bulk, a gigabyte would cost about $20k. This is, price-wise, equivalent to:

- RAM, in 1996

- Spinning disk, in about 1988

- Flash, in about 1998 (extrapolation, my chart doesn't have nay data before 2004).

Ref: http://www.jcmit.com/memoryprice.htm

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Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#42

Post by mmf »

I did research in the field from 2008 to 2013. The claims are always the same: faster than flash, denser than dram, lower power than both.

Here's how to spot BS: first, the density claims are immaterial until they prove yield at a technology node same as dram's today. There are multiple billions investment between 180nm and high yield (and low mask count) 2xnm, no matter how cool is the new memory technology.

Second, speed claims must be explicitly about latency: flash bandwidth is as large as you want it, latency is ~100us (read). Even so, the moment anybody claims that latency is faster than Dram, you know they're feeding the hype and lying to you: dram latency does not depend on the memory technology, rather it depends on the array size. So an 8Gb chip of any memory technology that is fast enough, is likely to be just as fast as dram.

Third: power consumption. Dram's active power is as low as it gets, the memory cell in particular stores information with really little energy. The array interconnect and circuitry consume most energy and a different memory technology won't change that.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#43

Post by tyho »

anotherangrydev wrote: post #9

Always the same thing. >1000X faster, 1000X cheaper! Then "No, you can't buy one right now, but you will be able to do it "soon". And, no it won't actually be 1000X faster neither 1000X cheaper because blah blah blah..."

I think the reason this is so often true, is because with stuff like this, there is not a eureka moment and suddenly you have something 1000x better than what already exists as can sometimes happen in other fields like chemistry, but a technique is developed and then improved over a period of time. The point being, nobody would wait to be 1000x better than the market, as soon as you beat the incumbents by a much lower factor, you will bring your product to market. There is no reason to hold your release because you are only at 10x and next year you will be 50x.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#44

Post by wmf »

Animats wrote: post #37

So what do we do with it? We have two models of storage - volatile working storage, and things that simulate disk drives. It's not clear what to do with persistent randomly addressable storage at DRAM speed. Having to go through an OS and a file system to access a few bytes kills the performance advantage of such devices. Making the device look like RAM makes it too easy to mess up. We need something in between, prob…

Coincidentally I noticed some recent patches on linux-kernel:

"BTT is a library that converts a byte-accessible namespace into a disk with atomic sector update semantics (prevents sector tearing on crash or power loss). ... BLK is a driver for NVDIMMs that provide sliding mmio windows to access persistent memory." https://lwn.net/Articles/649588/

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#45

Post by davrosthedalek »

wtallis wrote: post #32
rosser wrote: post #30

Earlier quoted context omitted.

"Bit-addressable". I don't think this suffers from the same issues that NAND does with successive writes. The other articles I'm seeing after a quick search also suggest a three order of magnitude increase in write endurance.

Yes, if you read what I wrote I mentioned the three orders of magnitude increase in write endurance as compared with NAND. But when paired with the three orders of magnitude increase in performance, that means it takes the same number of hours to burn it out. And a NAND device without wear leveling can be burned out in less than a day of heavy use. Bit addressability has absolutely nothing to do with endurance. NOR f…

The thing about bit addressability is not completely true. If you can address memory only in pages, you can have quite a large write amplification, depending on the access pattern. A single byte written may count as $PAGESIZE "written data".

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#46

Post by davrosthedalek »

wtallis wrote: post #33
DasIch wrote: post #28

Earlier quoted context omitted.

Interesting. At 128GB it's definitely practical to put your system partition and applications on it. If you rely heavily on cloud services that would be more than sufficient for most people and even if it isn't you could add an SSD for music and videos. If they release it next year and it turns out well, I can certainly see Apple pulling such a move for the MacBook (Air).

128Gb, not 128GB. You still need quite a few chips to build a usefully large drive.

128Gb is only a small factor below state-of-the-art flash chips, if at all. I think 3d NAND drives it up to 384 Gbit/die. Don't know about the die size though.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#47

Post by p1esk »

simpsond wrote: post #24
minthd wrote: post #12

A guess: this uses memristors(i.e. rram). crossbar is a startup in the field, their site gives plenty of details about the tech. http://www.crossbar-inc.com/

Do memristors read or write based on the applied voltage? I noticed that in some of the intel marketing material.

How else would you do read/write?

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#48

Post by Symmetry »

mmf wrote: post #42

I did research in the field from 2008 to 2013. The claims are always the same: faster than flash, denser than dram, lower power than both. Here's how to spot BS: first, the density claims are immaterial until they prove yield at a technology node same as dram's today. There are multiple billions investment between 180nm and high yield (and low mask count) 2xnm, no matter how cool is the new memory technology. Second,…

I think IBM found that the last level cache in their Power7 CPUs were faster with eDRAM than with SRAM because the reduction in transmission latency enabled by the smaller size made up for the higher cell latency so that's probably the crossover point where cell density wins over reasonable cell latencies. Of course memories with very large latency operations like a Flash erase can still dominate at much large sizes. And for off-die memory the transport is going to mask most differences anyways.

The various sort of stacked memory coming into commercial use have the potential to reduce interconnect power and potentially make active RAM power at least slightly relevant. But I think the interesting thing about reducing RAM power consumption is decreasing passive power. Not that I expect anything to come of it for at least another half decade.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#49

Post by russdill »

mmf wrote: post #42

I did research in the field from 2008 to 2013. The claims are always the same: faster than flash, denser than dram, lower power than both. Here's how to spot BS: first, the density claims are immaterial until they prove yield at a technology node same as dram's today. There are multiple billions investment between 180nm and high yield (and low mask count) 2xnm, no matter how cool is the new memory technology. Second,…

Actually you should be taking the claims very seriously. This has been an area Micron has been researching for decades. They've had a patent on the memory cell for about 11 years now (US6777705). Phase change memory has for a very long time been one of those just over the horizon technologies, but Micron has perfected it well enough to compete with NAND and partnered with Intel to bring it to market.

This isn't something that appeared out of nowhere. Take a look at this presentation:

https://www.micron.com/~/media/documents/products/presentati...

Page 20 starts the section on "3-D Cross-Point Memory". They even have a 64Mb demonstrator on page 23, fabbed sometime before the 2011 Flash Memory Summit.

Additional info on 64Mb demonstrator: http://investors.micron.com/releasedetail.cfm?releaseid=4672...

Additionally, in early 2014, they stopped selling PCM modules, stating that "Micron's previous two generations of PCM process technologies are not available for new designs or technology evaluation, as the company is focused on developing a follow-on process to achieve lower cost per bit, lower power and higher performance."

Job description details mentioning PCM, chalcogenides, and "cross point technology":

https://www.linkedin.com/jobs2/view/12292797?trk=job_view_si...

And as far as process, as early as 2013 (2013 fall analyst conference handouts), Micron had PCM on a 45nm process and was listing 2xnm as next node. If they've gotten together with Intel and announced this, they have already reached 2xnm and/or beyond or are certain in their capability to do so.

Because of the way flash memory is organized into pages and blocks, latency is very workload specific. Can you point out where anyone claimed it was better than DRAM latency?, the BBC article says "DRAM chips are still faster than 3D Xpoint, but the difference is much smaller than when compared with flash".

And power consumption. This is PCM. Power consumption by the array when not being read/written is zero.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#50

Post by zxcv123 »

mmf wrote: post #42

I did research in the field from 2008 to 2013. The claims are always the same: faster than flash, denser than dram, lower power than both. Here's how to spot BS: first, the density claims are immaterial until they prove yield at a technology node same as dram's today. There are multiple billions investment between 180nm and high yield (and low mask count) 2xnm, no matter how cool is the new memory technology. Second,…

Power consumption of DRAM is high, what are you talking about? DRAM requires constant refresh -- the whole reason DRAM can be high-density if because it is a 1-T cell with a trench capacitor -- but the capacitor needs to be refreshed on a synchronized basis (hence SDRAM) -- that was the big innovation.

And yes, array size affects latency but so does the underlying process technology (much more so across technologies).

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