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this post was submitted on 04 Aug 2023
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Explain Like I'm Five
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They both use entirely different technologies to store data. RAM is basically just a transistor and a capacitor used to store each bit. This makes it extremely fast to access but it requires a constant supply of power or that capacitor will just discharge. There really isn’t that much that can wear out using a capacitor and transistor so they have long lifespans.
SSDs use NAND flash. Basically they trap some electrons in an insulated section (the gate of a floating gate MOSFET) and to read that they measure the electric field caused by those electrons. This wears out because sometimes electrons may unintentionally quantum tunnel into the insulated section and become permanently trapped there. And once enough electrons have become permanently trapped there, you can no longer distinguish between different values.
You can’t use RAM technology in SSDs because it’s volatile - when power is removed all data gets wiped. It’s also much less dense than NAND flash. 1TB SSDs are pretty easy to find but when was the last time you saw a 1TB RAM stick at a reasonable price?
Do SD cards and usb sticks also use NAND?
Yes but usually cheaper/lower quality.
Any solid-state media you can access is almost certainly NAND. There's a second kind of flash memory called NOR, but it's gradually disappearing. I think it's relegated to EEPROMs and similar embedded uses. The number of applications where its advantages matter are outweighed by the seventeen bajillion dollar market for higher-capacity NAND. All the research money and foundry tech are going toward the one that'll let them sell 1 TB SSDs for $20.