Phase-change memory (PCM)
Beginner
A memory cell made of a material that can be glassy or crystal. The two forms let electricity through in different amounts.
Novice
A non-volatile memory whose cell material switches between an amorphous (high-resistance) and crystalline (low-resistance) state when heated by current pulses. Partial states give intermediate conductances that can store analog weights.
Expert
Conductance drifts after programming roughly as , with varying by state and device, so analog PCM chips compensate globally and use two devices per weight to raise SNR.
Explained in Sparsity, in-memory and analog compute (Architectures).
See also: RRAM (resistive RAM), Conductance drift.