Memory and Database

Saturday, November 18, 2006

History of Internal Memory Technologies

Examples of the first internal memory technologies used in computers in the early 1950's:



ELECTROSTATIC MEMORY
: Electrostartic storage tubes used in the Whirlwind computer in 1950 held a whopping 256 bits each. The bits were "painted" on the surface of the tube, and their electrostatic charges determined their content.



DELAY LINE MEMORY
: During the late 1940's and early 1950's, the memory in the EDSAC (Electrical Delay Storage Automatic Calculator) and UNIVAC I was made of tubes of liquid mercury that were several feet long. Electrical pulses were converted to sound and back to electrical in a continuous loop. The conversion to sound, which propagates much slower than electricity, slowed down the digital data a fraction of a second and caused the device to funciton as storage.



EDSAC: Developed by Maurice Wilkes at Cambridge University in England and completed in 1949. It was one of the first stored program computers and one of the first to use binary digits. Its memory was 512 36-bit words of liquid mercury delay lines, and its input and output were provided by paper tape. It could do about 700 additions per second and 200 multiplicaitons per second.



MAGNETIC DRUM MEMORY: This type of memory is in the IBM 650 Computer, introduced in 1954. It held two thousand 10-digit words. That much memory today would fit on the head of a pin, and a very thin pin to be sure.




MAGNETIC CORE MEMORY: Two years after the Magnetic Drum Memory, the tubes in the Whirlwind were replaced with magnetic cores, which were much more reliable. The direction of the magnetic energy in the core determined the 0 or 1. These core planes held 256 bits.



12 BITS
: Close up image of the Whirlwind core plane, shows the detail of the wiring between the cores.

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