Bendix G-20
Encyclopedia
The Bendix G-20 computer was introduced in 1961 by the Bendix Corporation
, Computer Division, Los Angeles, California. The G-20 followed the highly successful G-15 vacuum tube computer. Bendix sold its computer division to Control Data Corporation
in 1963, effectively terminating the G-20.
The G-20 system was a general purpose mainframe computer
, constructed of transistorized modules and core memory. Word size was 32 bits, plus parity. Up to 32k words of memory could be used. Single and Double precision floating point were allowed, as well a custom scaled format, called Pick-a-Point. A special form of the pick-a-point allowed an integer.
Memory locations 1 through 63 were used as index registers. One hundred and ten instructions were in the instruction set. The CPU included integral block I/O and interrupt facilities. Multiply time was 51-63 microseconds, and divide time was 72-84 microseconds. Basic memory cycle time was 6 microseconds.
in the 1960s. Usually the two processors ran independently, one CPU handling card-based input, and the other handling jobs submitted through one of 16 AT&T Dataphones connected to telephone lines, usually via Teletype
35 KSR, 35 ASR and Model 33 ASR teleprinters. The G-21 had 32k words of memory for each processor, but could be reconfigured for 64k mode for large programs, usually as a single processor. A true dual processor operating system was developed late in the life of the G-21, but never reached production status.
Another feature of the G-21 system was its high speed Philco "Scopes" system - when punch cards or 33 ASR Teletypes were the common form of I/O, this CRT
system allowed for a CRT display of information - and the "SpaceWar" game. Here, each operator saw the other player's ships on his screen. Buttons were used for thrust, spin, and firing missiles. The G-21 would play chess with you, via the teletype.
The directory system was called AND - Alpha Numeric Directory. Teleprocessing users could store programs on disks, tapes, or the RCA RACE mass storage unit interfaced through an RCA 301 computer. Users could retrieve and edit programs through AND. The 1-inch magnetic tapes were block addressable, allowing AND to manage a directory file system interchangeably on any available magnetic storage (tape, disk, or RACE cards).
The machine was programmed in a dialect of ALGOL
-60 called ALGOL-20. Deviations from Algol-60 included the lack of support for recursion, extensions to imbed G-20 machine language within ALGOL - WHAT, and a CIT developed printer formating language. Another language was GATE - the General Algebraic Translator Extended. It also used IPL-V (Newell's Information Processing Language-5) and Linear IPL-V as well as COMIT, and the assembler THAT. MONITOR was the supervisory program, and the special set of routines was called THEM THINGS.
An exposition of the G-21 design appears in a Carnegie Mellon webcast by the designer, Jesse Quatse, at CMU CS50. http://www.cs50.cs.cmu.edu/inside.php?page_id=42
Bendix Corporation
The Bendix Corporation was an American manufacturing and engineering company which during various times in its 60 year existence made brake systems, aeronautical hydraulics, avionics, aircraft and automobile fuel control systems, radios, televisions and computers, and which licensed its name for...
, Computer Division, Los Angeles, California. The G-20 followed the highly successful G-15 vacuum tube computer. Bendix sold its computer division to Control Data Corporation
Control Data Corporation
Control Data Corporation was a supercomputer firm. For most of the 1960s, it built the fastest computers in the world by far, only losing that crown in the 1970s after Seymour Cray left the company to found Cray Research, Inc....
in 1963, effectively terminating the G-20.
The G-20 system was a general purpose mainframe computer
Mainframe computer
Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...
, constructed of transistorized modules and core memory. Word size was 32 bits, plus parity. Up to 32k words of memory could be used. Single and Double precision floating point were allowed, as well a custom scaled format, called Pick-a-Point. A special form of the pick-a-point allowed an integer.
Memory locations 1 through 63 were used as index registers. One hundred and ten instructions were in the instruction set. The CPU included integral block I/O and interrupt facilities. Multiply time was 51-63 microseconds, and divide time was 72-84 microseconds. Basic memory cycle time was 6 microseconds.
G-21 system
A special configuration of the G-20, a dual processor G-21, was used to support campus computing at Carnegie Institute of TechnologyCarnegie Institute of Technology
The Carnegie Institute of Technology , is the name for Carnegie Mellon University’s College of Engineering. It was first called the Carnegie Technical Schools, or Carnegie Tech, when it was founded in 1900 by Andrew Carnegie who intended to build a “first class technical school” in Pittsburgh,...
in the 1960s. Usually the two processors ran independently, one CPU handling card-based input, and the other handling jobs submitted through one of 16 AT&T Dataphones connected to telephone lines, usually via Teletype
Teletype Corporation
The Teletype Corporation, a part of American Telephone and Telegraph Company's Western Electric manufacturing arm since 1930, came into being in 1928 when the Morkrum-Kleinschmidt Company changed its name to the name of its trademark equipment...
35 KSR, 35 ASR and Model 33 ASR teleprinters. The G-21 had 32k words of memory for each processor, but could be reconfigured for 64k mode for large programs, usually as a single processor. A true dual processor operating system was developed late in the life of the G-21, but never reached production status.
Another feature of the G-21 system was its high speed Philco "Scopes" system - when punch cards or 33 ASR Teletypes were the common form of I/O, this CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
system allowed for a CRT display of information - and the "SpaceWar" game. Here, each operator saw the other player's ships on his screen. Buttons were used for thrust, spin, and firing missiles. The G-21 would play chess with you, via the teletype.
The directory system was called AND - Alpha Numeric Directory. Teleprocessing users could store programs on disks, tapes, or the RCA RACE mass storage unit interfaced through an RCA 301 computer. Users could retrieve and edit programs through AND. The 1-inch magnetic tapes were block addressable, allowing AND to manage a directory file system interchangeably on any available magnetic storage (tape, disk, or RACE cards).
The machine was programmed in a dialect of ALGOL
ALGOL
ALGOL is a family of imperative computer programming languages originally developed in the mid 1950s which greatly influenced many other languages and became the de facto way algorithms were described in textbooks and academic works for almost the next 30 years...
-60 called ALGOL-20. Deviations from Algol-60 included the lack of support for recursion, extensions to imbed G-20 machine language within ALGOL - WHAT, and a CIT developed printer formating language. Another language was GATE - the General Algebraic Translator Extended. It also used IPL-V (Newell's Information Processing Language-5) and Linear IPL-V as well as COMIT, and the assembler THAT. MONITOR was the supervisory program, and the special set of routines was called THEM THINGS.
An exposition of the G-21 design appears in a Carnegie Mellon webcast by the designer, Jesse Quatse, at CMU CS50. http://www.cs50.cs.cmu.edu/inside.php?page_id=42
Equipment list, circa 1965/66
- CC-11 Real time clock and auxiliary console
- CP-11 Central Processor (2)
- MM-10 Memory Module (1)
- MM-11 Memory Module (7)
- MM-12 Memory Module, modified to work with display system
- DM-11 Disk unit
- TC-10 Tape Control Unit (2)
- MT-10 Magnetic Tape Unit, used 1" tape (8)
- PT-10 Paper Tape Unit
- SE-10 Teletype buffer
- LP-12 high speed line printer (2)
- LP-10 low speed line printer
- 3 display consoles, and 1 display controller.
- An IBM 1402 card reader/punch was used for batch job submission.