In the 60s/70s, an EE/CS guy named Leon Chua did some clever math that suggested we could build transistor-like devices that had a non-linear relationship between charge and flux and called it a memristor. He didn't build one, and as far as I know it's not something he's spent all that much time on since.

In the 90s somebody at HP must have mentioned memristors in hearing range of their marketing department and suddenly HP was going to have a product to market in a few years.

Yeah. Never happened. Nobody's done it.

In theory, such a device could allow us to do things like build extremely low power non-volatile memory (a flash replacement, basically). A lot of marketing hype has talked about completely replacing computer RAM with non-volatile memristor-backed memory, but again, neither it nor anything like it has happened. But as it turns out, battery-backed DRAM covers a multitude of sins anyway.

The actual debate over physical possibility is because it's too low-power, to the point that an actual implementation might violate lower theoretical limits on the amount of energy required to change the state of a bit. In other words, it might violate the second law of thermodynamics, which is something of a problem.

Yes, memristors are real, and no, their properties are not magic[1]. As I stated elsewhere on this thread, you can even make them at home[2]. It's even been discussed here on Hacker News before[3].

[1] https://electronics.stackexchange.com/questions/76097/what-a...

[2] http://sparkbangbuzz.com/memristor/memristor.htm

[3] https://news.ycombinator.com/item?id=9853984

They are real if you accept the branding of of companies trying to sell products that don’t really do much to people who are lured in by buzzwords. Those of us who actually do real work have serious doubts.

The original hypothesis was based on the existent resistor, capacitor, and inductor. The memristor would complete the symmetry between these components and the underlying physics.

https://en.wikipedia.org/wiki/Memristor#Background

And I'm going to assume GP is basically referring to the first paragraph of the next session regarding definition and criticism:

According to the original 1971 definition, the memristor was the fourth fundamental circuit element, forming a non-linear relationship between electric charge and magnetic flux linkage. In 2011, Chua argued for a broader definition that included all 2-terminal non-volatile memory devices based on resistance switching.[2] Williams argued that MRAM, phase-change memory and ReRAM were memristor technologies.[21] Some researchers argued that biological structures such as blood[22] and skin[23][24] fit the definition. Others argued that the memory device under development by HP Labs and other forms of ReRAM were not memristors, but rather part of a broader class of variable-resistance systems,[25] and that a broader definition of memristor is a scientifically unjustifiable land grab that favored HP's memristor patents.[26]

Read https://www.nature.com/articles/s41598-018-29394-7

This paper rejects the existing definitions of memristors as in inappropriate expression (composition) of devices using magnetic flux and inductance. It really doesn't cover the systems that use electrically adjustable resistance.