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Bendix G-15
The Bendix G-15 is a computer introduced in 1956 by the Bendix Corporation, Computer Division, Los Angeles, California. It is about 5 ft × 3 ft × 3 ft (1.52 m × 0.91 m × 0.91 m) and weighs about 966 lb (438 kg). The G-15 has a drum memory of 2,160 29-bit words, along with 20 words used for special purposes and rapid-access storage. The base system, without peripherals, cost $49,500. A working model cost around $60,000 (equivalent to $693,929 in 2024). It could also be rented for $1,485 per month. It was meant for scientific and industrial markets. The series was gradually discontinued when Control Data Corporation took over the Bendix computer division in 1963.
The chief designer of the G-15 was Harry Huskey, who had worked with Alan Turing on the Automatic Computing Engine (ACE) in the United Kingdom and on the Standards Western Automatic Computer (SWAC) in the 1950s. He made most of the design while working as a professor at University of California, Berkeley (where his graduate students included Niklaus Wirth), and other universities. David C. Evans was one of the Bendix engineers on the G-15 project. He would later become famous for his work in computer graphics and for starting up Evans & Sutherland with Ivan Sutherland.
The G-15 was inspired by the Automatic Computing Engine (ACE). It is a serial-architecture machine, in which the main memory is a magnetic drum. It uses the drum as a recirculating delay-line memory, in contrast to the analog delay line implementation in other serial designs. Each track has a set of read and write heads; as soon as a bit is read off a track, it is re-written on the same track a certain distance away. The length of delay, and thus the number of words on a track, is determined by the spacing of the read and write heads, the delay corresponding to the time required for a section of the drum to travel from the write head to the corresponding read head. Under normal operation, data are written back without change, but this data flow can be intercepted at any time, allowing the machine to update sections of a track as needed.
This arrangement allows the designers to create "delay lines" of any desired length. In addition to the twenty "long lines" of 108 words each, there are four more short lines of four words each. These short lines recycle at 27 times the rate of the long lines, allowing fast access to frequently needed data. Even the machine's accumulators are implemented as drum lines: Three double-word lines are used for intermediate storage and double-precision addition, multiplication, and division in addition to a one single-word accumulator. This use of the drum rather than flip-flops for the registers helped to reduce vacuum tube count.
A consequence of this design is that, unlike other computers with magnetic drums, the G-15 does not retain its memory when it is shut off. The only permanent tracks are two timing tracks recorded on the drum at the factory. The second track is a backup, as the tracks are liable to erasure if one of their amplifier tubes were to short-circuit.
The serial nature of the G-15's memory was carried over into the design of its arithmetic and control circuits. The adders work on one binary digit at a time, and even the instruction word was designed to minimize the number of bits in an instruction that needed to be retained in flip-flops (to the extent of leveraging another one-word drum line used exclusively for generating address timing signals).
The G-15 has 180 vacuum tube packs and 3000 germanium diodes. It has a total of about 450 tubes, mostly dual triodes. Its magnetic drum memory holds 2,160 words of twenty-nine bits. Average memory access time is 14.5 milliseconds, but its instruction addressing architecture can reduce this dramatically for well-written programs. Its addition time is 270 microseconds, not counting memory access time. Single-precision multiplication takes 2,439 microseconds and double-precision multiplication takes 16,700 microseconds.
One of the G-15's primary output devices is the typewriter with an output speed of about 10 characters per second for numbers (and lower-case hexadecimal characters u-z) and about three characters per second for alphabetic characters. The machine's limited storage precludes much output of anything but numbers; occasionally, paper forms with pre-printed fields or labels were inserted into the typewriter. A faster typewriter unit was also available.
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Bendix G-15 AI simulator
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Bendix G-15
The Bendix G-15 is a computer introduced in 1956 by the Bendix Corporation, Computer Division, Los Angeles, California. It is about 5 ft × 3 ft × 3 ft (1.52 m × 0.91 m × 0.91 m) and weighs about 966 lb (438 kg). The G-15 has a drum memory of 2,160 29-bit words, along with 20 words used for special purposes and rapid-access storage. The base system, without peripherals, cost $49,500. A working model cost around $60,000 (equivalent to $693,929 in 2024). It could also be rented for $1,485 per month. It was meant for scientific and industrial markets. The series was gradually discontinued when Control Data Corporation took over the Bendix computer division in 1963.
The chief designer of the G-15 was Harry Huskey, who had worked with Alan Turing on the Automatic Computing Engine (ACE) in the United Kingdom and on the Standards Western Automatic Computer (SWAC) in the 1950s. He made most of the design while working as a professor at University of California, Berkeley (where his graduate students included Niklaus Wirth), and other universities. David C. Evans was one of the Bendix engineers on the G-15 project. He would later become famous for his work in computer graphics and for starting up Evans & Sutherland with Ivan Sutherland.
The G-15 was inspired by the Automatic Computing Engine (ACE). It is a serial-architecture machine, in which the main memory is a magnetic drum. It uses the drum as a recirculating delay-line memory, in contrast to the analog delay line implementation in other serial designs. Each track has a set of read and write heads; as soon as a bit is read off a track, it is re-written on the same track a certain distance away. The length of delay, and thus the number of words on a track, is determined by the spacing of the read and write heads, the delay corresponding to the time required for a section of the drum to travel from the write head to the corresponding read head. Under normal operation, data are written back without change, but this data flow can be intercepted at any time, allowing the machine to update sections of a track as needed.
This arrangement allows the designers to create "delay lines" of any desired length. In addition to the twenty "long lines" of 108 words each, there are four more short lines of four words each. These short lines recycle at 27 times the rate of the long lines, allowing fast access to frequently needed data. Even the machine's accumulators are implemented as drum lines: Three double-word lines are used for intermediate storage and double-precision addition, multiplication, and division in addition to a one single-word accumulator. This use of the drum rather than flip-flops for the registers helped to reduce vacuum tube count.
A consequence of this design is that, unlike other computers with magnetic drums, the G-15 does not retain its memory when it is shut off. The only permanent tracks are two timing tracks recorded on the drum at the factory. The second track is a backup, as the tracks are liable to erasure if one of their amplifier tubes were to short-circuit.
The serial nature of the G-15's memory was carried over into the design of its arithmetic and control circuits. The adders work on one binary digit at a time, and even the instruction word was designed to minimize the number of bits in an instruction that needed to be retained in flip-flops (to the extent of leveraging another one-word drum line used exclusively for generating address timing signals).
The G-15 has 180 vacuum tube packs and 3000 germanium diodes. It has a total of about 450 tubes, mostly dual triodes. Its magnetic drum memory holds 2,160 words of twenty-nine bits. Average memory access time is 14.5 milliseconds, but its instruction addressing architecture can reduce this dramatically for well-written programs. Its addition time is 270 microseconds, not counting memory access time. Single-precision multiplication takes 2,439 microseconds and double-precision multiplication takes 16,700 microseconds.
One of the G-15's primary output devices is the typewriter with an output speed of about 10 characters per second for numbers (and lower-case hexadecimal characters u-z) and about three characters per second for alphabetic characters. The machine's limited storage precludes much output of anything but numbers; occasionally, paper forms with pre-printed fields or labels were inserted into the typewriter. A faster typewriter unit was also available.
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