price has been going down. In 2018, a "key characteristic of the DRAM market is that there are currently only three major suppliers — Micron Technology, SK Hynix and Samsung Electronics" that are "keeping a pretty tight rein on their capacity.” There is also Kioxia (previously Toshiba Memory Corporation after 2017 spin-off). Other manufactures make and sell DIMMs (but not the DRAM chips in them), such as Kingston Technology, and some manufacturers that sell stacked DRAM (used e.g in the fastest exascale supercomputers), separately such as Viking Technology. Others sell such integrated into other products, such as Fujitsu into its CPUs, AMD in GPUs, and Nvidia, with HBM2 in some of their GPU chips. History The cryptanalytic machine code-named "Aquarius" used at Bletchley Park during World War II incorporated a hard-wired dynamic memory. Paper tape was read and the characters on it "were remembered in a dynamic store. ... The store used a large bank of capacitors, which were either charged or not, a charged capacitor representing cross (1) and an uncharged capacitor dot (0). Since the charge gradually leaked away, a periodic pulse was applied to top up those still charged (hence the term 'dynamic')". In 1964, Arnold Farber and Eugene Schlig, working for IBM, created a hard-wired memory cell, using a transistor gate and tunnel diode latch. They replaced the latch with two transistors and two resistors, a configuration that became known as the Farber-Schlig cell. That year they submitted an invention closure, but it was initially rejected. In 1965, Benjamin Agusta and his team at IBM created a 16-bit silicon memory chip based on the Farber-Schlig cell, with 80 transistors, 64 resistors, and 4 diodes. The Toshiba "Toscal" BC-1411 electronic calculator, which was introduced in November 1965, used a form of capacitive DRAM (180 bit) built from discrete bipolar memory cells. The earliest forms of DRAM mentioned above used bipolar transistors. While it offered improved performance over magnetic-core memory, bipolar DRAM could not compete with the lower price of the then-dominant magnetic-core memory. Capacitors had also been used for earlier memory schemes, such as the drum of the Atanasoff–Berry Computer, the Williams tube and the Selectron tube. In 1966, Dr. Robert Dennard at the IBM Thomas J. Watson Research Center was working on MOS memory and was trying to create an alternative to SRAM which required six MOS transistors for each bit of data. While examining the