Bull Gamma 60

[3][4] Despite its innovations, the Gamma 60's large footprint (close to 4000 sq.ft), high cost, energy consumption, and complexity ultimately resulted in limited commercial success, with about only twenty units sold worldwide.

[7] Its architectural core was based on a large, high-speed central memory, with an arbitrator (known as the Program Distributor) responsible for distributing data and instructions to the various units within the computer.

[4] The processor operated in a 24-bit parallel configuration, with its primary data types employing one, two, or four words, also referred to as 'catenae', ranging from 24 to 96 bits in width.

All messages were asynchronous, and the machine, through priority classes, was designed to accommodate very high device latencies if necessary, even from an ALU (Arithmetic Logic Unit).

Given the distribution of processing units across separate cabinets, the choice of a slower clock speed of 100 kHz, half of what was originally envisioned, was aimed at mitigating the impact of propagation delays.

Additionally, it shared similarities with EPIC architectures such as Intel Itanium, in that each instruction was its own thread, and the management of execution concurrency and memory access coherence was placed under the responsibility of the programmer.

The sequencing mechanism employed by the Gamma 60 encompassed an orchestration of instruction fetching and distribution, execution control, memory access, and inter-process communication.

[7] This absence of advanced high-level tools for breaking down tasks into small concurrent threads meant that most programs only utilized a fraction of the hardware's capabilities.

It was delivered as a compact resident supervisor stored on magnetic tape, containing a bootloader, resource table, error handler and an operator command interpreter.

[7] A more advanced operating system, GGU (Gestion Générale des Unités), was later shipped but remained incomplete as the computer neared the end of its lifespan.

[6] Unfortunately, the software tools available in the late fifties and early sixties, such as compilers, operating systems, and debuggers, were still too primitive to fully utilize the capabilities of the Gamma 60.

Compilers allowing automatic exploitation of concurrency for an EPIC architecture only emerged in the late 1990s, after a development period that exceeded the entire lifespan of the Gamma 60.

[5] Due to the significant challenges in program development with the crude tools of the times, Bull lost several clients to IBM, whose machines, while single-processor, were simpler and more cost-effective.

[15] About twenty large companies and organizations showed interest in the Gamma 60 in the late fifties and early sixties, although not all of them made a purchase.

Other clients are listed in the table below:[15] (now BNP Paribas) The Régie des Télégraphes et Téléphones, later known as Belgacom and now Proximus, boasted one of the largest Gamma 60 installation, featuring an average of twenty Processing Units.

[6] Bull committed significant resources to the development of the Gamma 60, even though the practical utilization of its architectural innovations would not become feasible until the 1980s or even the 1990s, greatly impacting its commercial success.

[8] The challenges it faced in the market led to financial difficulties that hindered the creation of a more accessible, scaled-down version suitable for smaller companies.

Core memory of the Gamma 60
Bull Gamma 60 console
Block diagram of the Gamma 60
Scale model of the RTT Gamma 60, on display at the NAM-IP Computer Museum in Namur, Belgium.
Scale model of the SNCF Gamma 60 formerly displayed at the Auteuil railway station near Paris.