UNIVAC Solid State

The UNIVAC Solid State was a 2-address, bi-quinary coded decimal computer, with memory on a rotating drum with 5000 signed 10 digit words, spinning at 17,667 RPM in a helium atmosphere. It was announced by Sperry Rand in December 1958, as a response to the IBM 650. It came in two versions: the Solid State 80 (IBM-style 80 column cards) and the Solid State 90 (Remington-Rand 90 column cards).

With 20 vacuum tubes, 700 transistors, and 3000 FERRACTOR amplifiers in its CPU, the Solid State was one of the first computers to use solid state components.

The system used a clock derived from a timing band recorded on the main storage drum. This signal was read and amplified, processed and sent to the driver tubes, a pair of 6146 power pentode output tubes. The output from these 6146 tubes then fed the main clock power amplifier consisting of six 4CX250B metal/ceramic power tetrode tubes running in push-pull/parallel, yielding an output of a kilowatt. The SS80/90 computer could be heard quite clearly in the AM broadcast band at 707Khz and 1414Khz. The 4CX250B Tetrodes used a grounded plate (Anode)due to forced aircooling requirements. Interestingly, this tube is still in demand by amatuer radio operators. The power supply output was -1.6KV for cathode supply and -800V screen grid supply. At 1.8A capacity! Such a potential could be quite lethal! This supply weighed nearly 100 pounds and was mounted at the very top of the power supply stack!

The line printer ran at 600 lines a minute and printing was initiated "on-the-fly". This means that the printable characters were distributed around a drum with letters, figures and punctuation marks being positioned at each column point and the drum made up of these elements was continuously rotating. As the desired character came up to the printing position (indicated by a timing arrangement on the end of the drum, an argon gas filled thyratron would "fire" and cause a magnet to call and present a small armature to the face of the printing paper with a ribbon similar to a typewriter ribbon interposed between the paper and the armature. As the armature was propelled forward onto the ribbon and the paper the character would be printed and immediately the armature would reset with a spring to await the next time the tube fired and the process would repeat on the next line down the sheet.

Timing was super critical throughout the operation of the card punch, the card reader and the printer, all being based on electromechanical principles. The basic card punch mechanism was manufactured by Bull, a French company with license to sell an 80 column punch. The machine came in a couple versions, the P147 and the P67, a main difference being electromagnetic clutch or a solenoid operated mechanical "dog" clutch to initiate a punch cycle. This machine was a difficult to maintain and required great mechanical talent to troubleshoot! It consumed much of the maintenance time.

ee also

*List of UNIVAC products
*History of computing hardware

External links

* [http://www.cc.gatech.edu/~randy/folklore/dec92-v1n2.html Unisys History Newsletter. Volume 1, Number 2, December 1992 (revised 1999) - The UNIVAC Solid State Computer]
* [http://www.bitsavers.org/pdf/univac/uss/ Univac Solid State Manuals and documentation]