The Flash Memory Lifespan Question: Why QLC May Be NAND Flash’s Swan Song

The late 1990s saw the widespread introduction of solid-state storage based around NAND Flash. Ranging from memory cards for portable devices to storage for desktops and laptops, the data storage future was prophesied to rid us of the shackles of magnetic storage that had held us down until then. As solid-state drives (SSDs) took off in the consumer market, there were those who confidently knew that before long everyone would be using SSDs and hard-disk drives (HDDs) would be relegated to the dust bin of history as the price per gigabyte and general performance of SSDs would just be too competitive.

Fast-forward a number of years, and we are now in a timeline where people are modifying SSDs to have less storage space, just so that their performance and lifespan are less terrible. The reason for this is that by now NAND Flash has hit a number of limits that prevent it from further scaling density-wise, mostly in terms of its feature size. Workarounds include stacking more layers on top of each other (3D NAND) and increasing the number of voltage levels – and thus bits – within an individual cell. Although this has boosted the storage capacity, the transition from single-level cell (SLC) to multi-level (MLC) and today’s TLC and QLC NAND Flash have come at severe penalties, mostly in the form of limited write cycles and much reduced transfer speeds.

So how did we get here, and is there life beyond QLC NAND Flash?

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That Old ThinkPad Needs An Open Source 2.5″ IDE SSD

So you fancy yourself a FOSS devotee, do you? Running GNU/Linux on your old ThinkPad, avoiding devices that need binary blobs? Got LibreBoot installed too? Not bad, not bad. But what about the hard drive? Can you be sure you aren’t leaking some freedoms out of that spinning rust?

Well, worry no more. Thanks to the work of [dosdude1], we now have an open source solid state drive that’s designed to work with any device which originally used a 2.5 inch IDE hard drive. The choice of releasing it under the GPL v3 versus an open hardware license might seem an odd choice at first, but turns out that’s actually what the GNU project recommends currently for circuit designs.

Fair warning: all the chips on the board are BGA.

Which is precisely what we’re talking about here — just a circuit design done up in KiCad. There’s no firmware required, and the PCB features very little beyond the four BGA152/BGA132 NAND flash chips and the SM2236 controller IC. You’ve just got to get the board fabricated, obtain (or salvage) the chips, and suddenly your retro laptop is sporting the latest in mass storage technology.

So how does it work? The SM2236 is actually a CompactFlash (CF) controller, and since IDE and CF interfaces are so similar, the PCB doesn’t have to do much to adapt from one to the other. Sprinkle in a few NANDs, and you’ve got yourself a native SSD suitable for old school machines. [dosdude1] says the board can slot four 64 GB chips, which should be more than enough given the age of the systems this gadget will likely be installed in. There are a few catches though: the NAND chips need to be supported by the SM2236, and they all have to match.

If you need something even smaller, [dosdude1] produced a 1.8 inch SSD using the same techniques back in October of last year.

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SSD Upgrade For 24″ IMac


The hard drive in [Jason’s] 24″ iMac was on the blink. He decided that instead of just swapping out the bad drive for a traditional unit he would upgrade to a solid state drive. Tearing apart high-end hardware like this can be a bit nerve-racking but luckily the drive is mounted right behind the screen so he didn’t have to take everything apart.

The SSD he picked up was 2.5″ but the mounting hardware in the iMac is only setup for 3.5″ form factors. We would have used a bit of hackery to make it work but [Jason] went with an adapter kit. Uh-oh, once installed there was no problem with the mounting but the SATA cable didn’t reach far enough to plug it in. The cable snaked around under the motherboard and would have been a lot of work to swap forĀ  a longer one. He ended up removing all of the mounting screws except for one coercing the drive close enough for the connection.

It worked for him and it can for you as well. If you do this make sure to devise your own mounting scheme so that you don’t hit the same snag.

[Photo: AppleInsider iMac teardown]

[via TUAW]