The Bendix G-15 was a mid-1950s, binary, vacuum-tube, drum-memory computer system. The system was designed by Harry Huskey for Bendix during 1952-1953, while at Wayne State University in Detroit, Michigan. It was first available to customers as the G-15A in 1956. The better-known G-15D was released in 1957.
Huskey had worked on Alan Turing's ACE computer and its prototype, the Pilot Ace, at the National Physical Laboratory in England during 1946-1947. The design of the G-15 was heavily influenced by the Pilot ACE, especially in its bit-serial operation, source-to-destination command structure, and its implementation of memory and registers as recirculating delay lines. The delay lines were implemented using the rotating magnetic drum rather than the mercury-filled tubes of the Pilot ACE.
The G-15 was an unusually small and inexpensive computer system for its day. The basic configuration consisted of a single cabinet and a modified IBM Model B electric typewriter. The cabinet was 61 inches high by 27 inches wide by 32 inches deep (155 x 69 x 81cm), weighing 950 pounds (430kg) -- about the size of a home refrigerator. It ran on standard U.S. 110-volt power, drew 38 amps (about 3KW RMS), and dissipated 14,300 BTU/hour of heat. It used approximately 450 vacuum tubes and 3000 germanium diodes.
The system had a 29-bit word. The drum held 2160 words in 20 108-word "long" lines (or tracks), plus 16 words in four 4-word "fast" lines. The single- and double-precision registers were also stored on the drum. The drum rotated at 1800 RPM. Average access time was approximately 15ms for the long lines and 0.5ms for the fast lines, although these times could be improved by carefully assigning locations on the drum to achive minimal rotational access delay. The clock rate was 108KHz.
An August 1957 price list indicates a basic G-15D system could be purchased for $49,500 USD or leased for $1,485 USD per month. In 2021 dollars, those prices would be approximately $477,000 and $14,300, respectively [source].
The basic G-15 system supported only paper-tape and typewriter input/output, and only hexadecimal data formatting. Decimal input and output were accomplished by means of software conversion routines. Optional peripherals included higher-speed paper-tape devices, a digital plotter, magnetic tape, an adapter for alphanumeric input/output (using a Flexowriter electric typewriter), adapters for IBM punched-card devices, and an adapter for custom data interfaces.
Over 400 systems were built, with about 300 installed in the United States, making it a successful and popular computer during the late 1950s and early 1960s. It was particularly popular with engineering departments for road and structural design calculations.
Bendix corporate headquarters were in Detroit, but the G-15 was manufactured and supported by the Bendix Computer Division in Los Angeles, California. Bendix sold its Computer Division to Control Data Corporation in 1963, but CDC supported the G-15 for only a couple of years after that. Some machines may still have been running as late as the early 1970s.
The main goals of this project are creation of a web browser-based emulator for the G-15D variant of the system and recovery of as much software for the system as we are able to find.
The contents of this project are licensed under the MIT License.
| Related Sites | URL |
|---|---|
| Emulator hosting site | http://www.phkimpel.us/Bendix-G15/ |
| Project Wiki | https://github.com/pkimpel/retro-G15/wiki/ |
| Project Blog | https://retro-emulation.blogspot.com/ |
| G-15 Documents at bitsavers | http://bitsavers.org/pdf/bendix/g-15/ |
| Huskey G-15 lecture | https://www.youtube.com/watch?v=flb6ha3XRw8 |
| David Green's G-15 site | https://www.uraone.com/computers/bendixg15/ |
| Paul Pierce's G-15 site | http://www.piercefuller.com/collect/bendix/ |
| G-15 Wikipedia page | https://en.wikipedia.org/wiki/Bendix_G-15 |