Ann: 4DS Achieves New Write Speed Milestone, page-297

Well, 4DS RERAM cells are programmable resistors. That can be fabbed on industry standard equipment

From the article:

Programmable resistors are the key building blocks in analog deep learning, just like transistors are the core elements for digital processors. By repeating arrays of programmable resistors in complex layers, researchers can create a network of analog artificial “neurons” and “synapses” that execute computations just like a digital neural network. This network can then be trained to achieve complex AI tasks like image recognition and natural language processing.