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Solid state non-volatile storage technologies such as NOR and NAND flash memory use something called floating-gate transistors [1]. Making these transistors is highly complex, and substantial amounts of research efforts have gone into R&D to improve NOR and NAND technologies.

A real issue with these memory technologies is wear. There is a finite amount of times a NOR/NAND gate can be written, and the implementation of wear leveling prolongs the lifespan of the memory device without solving the root issue.

Optane memory (originally called 3D XPoint) starts getting closer to the theoretical ideal of a memristor. According to [2], Optane allows a "memory cell to be written to or read without requiring a transistor." It's still not entirely sure what's the enabling technology, but the general consensus is that Optane is a form of resistive RAM, or ReRAM [3]. Not quite the memristor, but it's edging toward it.

Why memristors? Imagine you're given a piece of conductive material which changes its resistivity based on net current flow over time. It's just a chunk of material, so manufacturing memory cells goes from etching transistors to material deposition. Also, you can likely make the memristors smaller than today's transistors, meaning higher storage densities. Additionally, the memory should be bit-addressable unlike block-addressed NAND. Also, the memristor is fundamentally an analog device, meaning there's the potential for interesting innovations in storage technology (analog storage elements?). Finally, energy consumption should be even lower than transistors.

Takeaways: - NOR/NAND storage is transistor-based and will eventually be replaced with neuromorphic technologies such as memristors. - Optane storage exhibits expected properties of a memristor, but it's not quite a true memristor.

[1] https://en.wikipedia.org/wiki/Flash_memory [2] https://www.anandtech.com/show/9541/intel-announces-optane-s... [3] https://en.wikipedia.org/wiki/3D_XPoint

Flash cells are analog as well - depending on the gate charge the resistance/current flow is different.

That's used for MLC/TLC.

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