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Working on Another Experiment: SSD Asynchronous vs. Synchronous NAND

Posted on March 16, 2014

I wanted to give everyone a quick update as to why the hardware features have been quiet since the unveiling of our dual- vs. single-channel RAM test a couple weeks back. There's been a lot of fuss lately about asynchronous NAND finding its way into a specific Kingston SSD that was previously known to use synchronous NAND. Most of the discussion was relegated to forums, where users ran somewhat haphazard benchmarks to determine that the new model of the V300 (using asynchronous NAND) was severely underperforming versus the earlier model that used a higher-quality NAND supply. I'll get into what this means briefly in a moment.


In short, it looks like the NAND type in the older V300 was Toshiba's 19nm Toggle-Mode 2.0 supply, which I've confirmed by opening our drive; the new NAND used in the newer iteration of the V300 -- which has no listing in the specs to make the difference clear -- is Micron's 20nm asynchronous NAND. The switch to asynchronous NAND allows the drive to be produced for much cheaper, but has an inherent performance detriment. If you're unsure of what I mean by "asynchronous" and "synchronous," it boils down to this:

The major NAND types being supplied to manufacturers are largely made by Toshiba, Micron, and Samsung. Samsung and Toshiba both make "Toggle-Mode" NAND, whereas the other suppliers make "ONFI" NAND, or "Open NAND Flash Interface," which has been developed by more than 100 companies and serves as a sort-of "open source" NAND. It's not exactly that simple nor that open, but that's the general idea.

Synchronous NAND operates faster on paper, but the translation to real-world benefit is directly dependent upon the controller used. We'll explore this in the impending article that I'm priming you for. Synchronous NAND uses a timing circuit that effectively transmits data twice on the signal wave (rise, fall), whereas asynchronous NAND moves data once. It looks something like this (image from Samsung):


And so synchronous NAND is generally what users vouch for and prefer. But, just like TLC vs. MLC, it isn't necessarily that simple -- and cost can absolutely play a key role in what NAND a consumer ends up with, especially when buying a budget drive like the V300.

My objective was to investigate Anandtech's article, which indicated that Kingston's new V300 should perform significantly, noticeably worse than their old V300 (we'll call them V300S and V300A - or Synchronous & Asynchronous).

All the tests are complete - I am presently in the stage of validating the results (a second and third test pass) and then compiling the data into charts for your consumption.

Oh, and as a quick side note, we will be in California for GDC & GTC as of tomorrow. Who wants to come pack for me while I finalize these tests?

- Steve "Lelldorianx" Burke.