Bull Gamma 3

The Gamma 3 is an electronic computer designed by Compagnie des Machines Bull and released in 1952.
Originally designed as an electronic accelerator for electromechanical tabulating machines, similar to the IBM 604, it was gradually enhanced with new features until it evolved into a first-generation stored program computer (Gamma ET, 1957).
Over the course of its ten-year career, this pivotal machine facilitated the transition from electromechanical unit records equipment to computers. The Gamma 3 was a commercial success, eventually selling more than 1200 units and prompting IBM to release the 1401 as a competitor.
==History==
Until the 1950s, Compagnie des Machines Bull, like its rival IBM, primarily marketed punched card tabulators for inventory management, payroll, and accounting.
These tabulators performed arithmetic operations through a series of digit wheels driven by an electro-mechanical device. Only incrementation, and thus addition, was supported, making subtractions and multiplications particularly slow.
In order to increase the calculation speed and avoid delaying the reading of punched cards during more complex operations, an accelerator capable of overcoming electro-mechanical limitations became a necessity.
Starting in 1949, the Bull Company became interested in vacuum tubes for their switching speed compared to adding wheels and electromechanical relays. The computer was designed using logical circuits comprising around 400 tubes, as well as germanium diodes and 7 delay lines with a 48-bit capacity for registers.
The machine was clocked at a frequency of 281 kHz, a higher speed than the 50 kHz of the IBM 604, and more importantly, several orders of magnitude faster than electromechanical devices. The execution time for additions was between 17 and 23ms, while multiplications took between 19 and 33ms. The Gamma 3 was connected to the tabulator through a cable plugged in place of its connection panel (where the program instructions were coded); thus, the program would now reside and run on the Gamma 3 computer rather than the tabulator.
Nevertheless, while the Gamma 3 was programmable through a removable connection panel similar to those of tabulators, it remained a peripheral device of the tabulator rather than the other way around. Furthermore, despite being electronic, binary, and programmable, the Gamma 3 still lacked the ability to store programs in memory.
A first step towards becoming a computer in a modern sense occurred with the Card Program (Programme Par Carte, PPC), introducing the capability to execute a program loaded from punched cards rather than hard wired onto a connection panel. IBM also experimented with a similar concept with the CPC (Card Programmed Calculator) extension added to the 604. However, the program was still not executed in main memory, which did not exist at that time, so its execution speed depended on the reading speed of the punched cards containing the program.
Finally, a magnetic drum memory was added in 1957, with a capacity of 49 to 98 kB (64 to 128 tracks of 8 blocks of 16 words of 48 bits), a fairly generous amount for that time. In addition, a standalone operator console was also included, featuring a small oscilloscope CRT display and push buttons to examine memory and single step the code. With the capability to load and execute programs in memory, the Gamma 3 ET (Extension Tambour, meaning Drum Extension) became the first French commercial stored program computer. The tabulator now served as an input/output device, while the Gamma ET became the central processing unit. Gradually, the electromechanical unit record equipment gave way to electronic computers.
The first client to receive a Gamma 3 was Crédit Lyonnais in Saint-Étienne in March 1953. The Gamma 3 and 3 ET were subsequently used both in business data processing within large companies and for scientific calculations, notably at the then-emerging CERN and CNRS.
The Gamma 3 ET positioned itself as a competitor to the IBM 650 computer, which had a very similar design.
==Historical and Technical Particularities==
Similar to the ENIAC, the Gamma 3 was born as a programmable electronic calculator before evolving into a stored-program computer.
The Gamma 3 features a dual-mode ALU, capable of operating both in decimal mode (12-character BCD words) for business data processing, or in binary mode (48-bit words) for industrial and scientific computing.
As an uncommon feature for the 1950s, the Gamma 3 was optionally equipped with a hardwired floating-point library. This model, known as Gamma 3M, was intended for scientific calculations.
In 1959, the first university programming courses in France were conducted using Gamma 3 ET machines by Professor Louis Bolliet. These courses are now available online and have been instrumental in the creation of Gamma 3 simulators.
The commercial success of the Gamma 3 prompted the creation of the IBM 1401 in response.
==Preservation==
Three examples of the Gamma 3 still exist today. One is exhibited at Technikum near Frankfurt, another at the Fédération des Équipes Bull in Angers, where it was manufactured. Lastly, ACONIT in Grenoble houses a unique specimen of the Gamma 3 ET.
Category:Computers
Category:Vacuum tube computers
Category:1952 in computing