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Invention of RAM
The first form of RAM came about in 1947 with the use of the Williams tube. It utilized a CRT (cathode ray tube); the data was stored on the face as electrically charged spots. It could hold a few hundred to a few thousand bits of data. -
Magnetic-Core Memory
Invented by An Wang in 1947 (shortly after CRT) Magnetic Core memory quickly overcame CRT RAM due to increased capacity and increased speeds. It wasn't widely adopted until 1955, however. Magnetic-Core Memory used rings of a hard magnetic material where wires would thread through the core and serve as a transformer winding. Three or four wires passed through each core while each core could store one bit of information. -
MOS RAM
Invented by John Shmidt in 1964, the MOS (Metal-Oxide-Semiconductor), provided higher speeds and was much cheaper to produce. Because of MOS RAM, we got the invention os SRAM which paved the way forward for all modern RAM we have today. -
Static RAM
Invented by Robert H. Norman shortly after the development of MOS SRAM, SRAM became an alternative to magnetic-core memory but required six MOS transistors for each bit of data. The commercial use of SRAM began in 1965 when IBM introduced the SP95 memory chip for the System/360 Model 95. -
Dynamic RAM
Invented in 1967 by Fujio Masuako, Dynamic random-access memory (DRAM) allowed replacement of a 4 or 6-transistor latch circuit by a single transistor for each memory bit, greatly increasing memory density at the cost of volatility. Data was stored in the tiny capacitance of each transistor and had to be periodically refreshed every few milliseconds before the charge could leak away. Today, all modern RAM is a variation of Dynamic/Static Ram.
