NVDIMM: Nonvolatile... Not NVIDIA

Subject: General Tech, Memory, Systems | February 10, 2013 - 12:44 AM |
Tagged: NVDIMM, micron, IMFT NAND, imft

So a RAM chip, a NAND module, and an “ultracapacitor” walk into stick...

This week Micron released a press blast for technology called, “NVDIMM”. The goal is to create memory modules which perform as quickly as DRAM but can persist without power. At this point you could probably guess the acronym: Nonvolatile Dual In-line Memory Module. It has been around for a few years now, but it is in the news now so let's chat about it.

I often like to play the game, “Was this named by an engineer or a marketer?” You can typically tell who was responsible for naming something by gauging how literally it breaks down into a simple meaning versus not having any apparent meaning at all. A good example of an engineer name is UHF, which breaks down into ultra-high frequency because it's higher than VHF, very-high frequency. A good example of a marketing name would be something like “Centrino”, which sounds like the biggest little penny-slot machine in the world. I would quite comfortable guessing that NVDIMM was named by an engineer.

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This is AgigA Tech's module, who provides the capacitors for Micron and their NVDIMMs.

The actual makeup of NVDIMMs is quite sensible: DIMMs are fast but die when the power goes out. You could prevent the power from going out but it takes quite a lot of battery life to keep a computer online for extended periods of time. NAND Flash is quite slow, relative to DIMMs, in normal operation but can persist without power for very long periods of time. Also, modern-day capacitors are efficient and durable enough to keep DIMMs powered for long enough to be copied to flash memory.

As such, if the power goes out: memory is dumped to flash on the same chip. When power is restored, DIMMs get reloaded and continue on their merry way.

According to the Micron press release, the first NVDIMM was demonstrated last November at SC12. That module contained twice as much NAND as it did DIMM memory: 8GB of Flash for 4GB of RAM. Micron did not specify why they required having that much extra Flash memory although my gut instinct is to compensate for write wearing problems. A two-fold increase to offset NAND that had just one too many write operations seems like quite a lot compared to consumer drives. That said, SSDs do not have to weather half of their whole capacity being written to each time the computer shuts down.

Who knows, double-provisioning might even be too little in practice.

Source: Micron
February 10, 2013 | 09:07 AM - Posted by orvtrebor

It's a great idea, And if I'm understanding the concept even if the power went out the data would be stored instantly onto the NAND so this would eliminate any chance of unsaved data loss?

I can't justify buying 32 gigs of ram (cost wise), but I would definitely pay extra for 8 or 16 with this feature.

February 10, 2013 | 06:33 PM - Posted by Roguekitsune (not verified)

Its a nice idea but i dont think its a solution that we need or should invest in. Flash memory has a limited life time and there is no telling when the Flash on there will die. Instead there should be more investments in advancing technologies such as MRAM(Magnetoresistive random access memory) and FeRAM(Ferroelectric random access memory). These solutions are non-volatile, have almost the same performance, and power consumption on par or lower than DRAM.

February 10, 2013 | 10:00 PM - Posted by Anonymous (not verified)

Agree whole heartily with above statements. Would have been a fascinating idea about a half decade ago, or maybe even longer although I don't think NAND dies would have been large enough back then.

Truth is, for the past decade research has been well underway for not only a replacement for NAND, but a replacement for DRAM. The convergence on that replacement is inevitable and quickly approaching as test chips are already being fabricated. Where that technology lies is another thing on its own, but the need for a new technology to replace both has been well underway and within that same 5 year period will most likely come to fruition. Even if this was mass produced starting tomorrow it would be a dead technology with maybe two generations of use before the replacement tech arrives. That's given it doesn't require a brand new redesign of the RAM slots currently in production.

ST-RAM and MRAM are here, today, and they will be the tomorrow soon enough. Shame this couldn't have been done 10 years ago.

February 12, 2013 | 12:43 PM - Posted by Anonymous (not verified)

How does this product work in practice without additional hardware or software to support saving and restoring the state of the CPU? Once the power is restored, how does the machine start functioning again without some type of process akin to coming out of hibernation? Does this memory contain extra memory to save the contents of the CPU registers and such?

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