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Engineers Devise a Technique To Fight Counterfeit or Recycled Smartphone Memory (ieee.org)
Flash is designed to last a decade or more of use. A lot of the gadgets that rely on it, however, are not. Shady recyclers have spotted opportunity in that mismatch, stripping out used chips and selling them as new. But fret not, there is something that can be done to address the issue. From a report: Engineers at the University of Alabama have come up with a straightforward electronic examination that can tell if a flash chip is new or recycled, even if that chip has only seen 5 percent or less of its life. And the technique is so straightforward that a smartphone app could run it on its own memory. [...] A flash memory cell is like an ordinary transistor, it has a source and a drain and a channel through which current flows under the control of voltage on the gate electrode. The difference is that the gate is split into several layers -- the control gate, the blocking oxide, the floating gate, and the tunneling oxide.
[...] Voltage on the control gate causes electrons to tunnel through that bottom oxide and get stuck inside the floating gate. This charge or its absence is the stored bit. It alters how much voltage you need to turn the transistor on in a way that you can easily measure. Erasing the bit is done by reversing the voltage and driving the charge out of the floating gate. Ray and his team took advantage of the rather high voltages -- about plus or minus 20 volts -- needed to program and erase flash. The more you program and erase a cell, the more defects will accumulate in the oxide, he explains.
[...] Voltage on the control gate causes electrons to tunnel through that bottom oxide and get stuck inside the floating gate. This charge or its absence is the stored bit. It alters how much voltage you need to turn the transistor on in a way that you can easily measure. Erasing the bit is done by reversing the voltage and driving the charge out of the floating gate. Ray and his team took advantage of the rather high voltages -- about plus or minus 20 volts -- needed to program and erase flash. The more you program and erase a cell, the more defects will accumulate in the oxide, he explains.
Wouldn't it be more productive to create positive channels for recycling the flash memory? There are plenty of usage cases where the reduced performance would be unimportant, and the reduced cost would be attractive. If you want to stop "shady recyclers," the obvious solution is to bring them into the sunlight.
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How much wear and tear does the flash memory in the typically device actually take? Now that that amount of RAM on these phones is sufficiently high (The newest Android flagships have 4 GB now) there shouldn't be as much need to use the flash memory for a pagefile or something of the sort. I'm not even using 64 GB on my phone (most of it is music which is just going to be read from) and that's what comes standard on most flagship devices these days.
I suspect that a lot of this used flash would still outlast the expected lifespan of the device for most people. I can even see the recycling companies using this technique themselves to sell the recycled chips in different bins based on use. The article doesn't describe the extent to which people are getting worn out flash memory, and I suspect it's not a particularly big issue.
"Why aren't we even trying to make designs that good? Instead all you get is stupid little gimmicks like rounded corners or notches in the screen."
Because having phones that last longer is in direct conflict with the motives of literally every competitor making phones. Even if they never sit in a room and collude they'll reach the same result simply by acting out of self-interest. Why would they compete with each other on more durable phones or in any real way on cost when those things hurt their bottom lines? Better to make everyone replace their phone on a regular basis and compete for pieces of the next round of purchases.
The notion that a smartphone app can do this test doesn't hold up to scrutiny. I don't think even the operating system could do it in most cases.
Both of the techniques described require the testing tool to be able to measure the effects of wiping or rewriting a given page. But modern flash hardware doesn't provide any way to operate on a specific physical page, only on logical pages which the hardware reallocates to different physical locations. Pretty much any time you try to erase a block of flash, what the hardware will really do is give you an already-erased block.
And, of course, apps don't have access even to logical blocks, they have to work through the file system. File systems designed for flash add another layer of shuffling, and even general-purpose file systems often do some amount of reallocation.
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