Editing GE-600 series (section)

==History==
The GE-600 line of computers was developed by a team led by [[John Couleur]] out of work they had done for the military [[MISTRAM]] project in 1959. MISTRAM was a [[radar]] tracking system that was used on a number of projects, including [[Project Apollo]]. The [[United States Air Force|Air Force]] required a data-collection computer to be installed in a tracking station downrange from [[Cape Canaveral]]. The data would eventually be shared with the 36-bit [[IBM 7094]] machine at the Cape, so the computer would likely have to be 36-bits as well. GE built a machine called the [[MISTRAM#M-236 computer|M236]] for the task, and as a result of the 36-bit needs, it ended up acting much like the 7094.

GE originally had not intended to enter the commercial computer market with their own machine. However, by the early 1960s GE was the largest user of [[IBM mainframe]]s,<ref>{{Cite web |title=GE-635 System Manual - Manual - Computing History |url=http://www.computinghistory.org.uk/det/15671/GE-635-System-Manual/ |access-date=2023-01-23 |website=www.computinghistory.org.uk}}</ref> and producing their own machines seemed like an excellent way to lower the costs of their computing department. In one estimate, the cost of development would be paid for in a single year free of IBM rental fees. Many remained skeptical, but after a year of internal wrangling, the project to commercialize the M236 eventually got the go-ahead in February 1963.

The machine was originally offered as the main '''GE-635''', and the slower but compatible '''GE-625''' and '''GE-615'''. While most were single-processor systems, the 635 could be configured with four CPUs and up to four input/output controllers (IOC's) each with up to 16 Common Peripheral Interface Channels. The 635 was likely the first example of a general purpose [[Symmetric multiprocessing|SMP]] system, though the GECOS/GCOS software treated the processors as a master and up to three slaves.

In August 1964, IBM considered the GE 600 series to be "severe competition in the medium and large-scale scientific areas".<ref>IBM DSD ASG memo, August 13, 1954, US v IBM, Exh 14791 p.386</ref> In May 1965 the first GE-625 computer was delivered to the GE Schenectady plant to replace five other computers of various sizes and makes.<ref>"Training for conversion". Mario V. Farina, Datamation, June 1966</ref>  A number of GE 635's were shipped during 1965 including two to Martin Marietta in November.<ref>Datamation, August 1965, p.71</ref>

The 600 line consisted of six models: the 605, 615, 625, 635, 645, and 655.  GE offered a box to connect to the 635 called a 9SA that allowed the 635 to run 7094 programs.

The 615 was a 635 with Control Unit (CU) and Operations Unit (OU) overlap disabled, and a 36-bit-wide memory path. The 625 was a 635 with Control Unit and Operations Unit overlap disabled and 72-bit-wide memory path. The 635 had a 72-bit-wide memory path and CU/OU overlap enabled. The difference between these models was fewer than 10 wires on the backplane. Field service could convert a 615 to a 635 or 625 or vice versa in a couple of hours if necessary; other than those few wires, the 615, 625 and 635 were identical. The 605 was used in some realtime/military applications and was essentially a 615 without the floating point hardware. Programs coded for a 605 would run without any modification on any other 600 line processor. The 645 was a modified 635 processor that provided hardware support for the [[Multics]] operating system developed at [[MIT]]. 

The 605/615/625/635 and 645 were essentially [[Transistor computer|second generation computers]]<ref name="Gandy2012">{{cite book |last1=Gandy |first1=Anthony |title=The Early Computer Industry: Limitations of Scale and Scope |date=30 November 2012 |publisher=Springer |isbn=978-0-230-38911-3 |pages=100–102 |url=https://books.google.com/books?id=viDGg4_NvPQC&pg=PA100 |access-date=24 September 2024 |language=en}}</ref> with discrete transistor [[Transistor–transistor logic|TTL logic]] and a handful of [[integrated circuit]]s. Memory consisted of a two-microsecond [[Magnetic-core memory|ferrite core]], which could be interleaved. GE bought core memory from [[Fabri-Tek]], [[Ampex]] and [[Lockheed Corporation|Lockheed]]. The Lockheed memory tended to be the most reliable.{{citation needed|date=December 2011}}

Continuing problems with the reliability of the [[magnetic tape]] systems used with the system cast a pall over the entire project. In 1966 GE withdrew the 600 series from active marketing, there was also widespread redundancies in the Phoenix operation, the issues with the 600 series damaged GE's reputation in the computer industry<ref name="Gandy2016">{{cite journal |last1=Gandy |first1=Anthony |last2=Edwards |first2=Roy |title=Enterprise logic vs product logic: the development of GE's computer product line |journal=Business History |date=11 Jul 2016 |volume=59 |issue=3 |pages=431–452 |doi=10.1080/00076791.2016.1205033|url=https://eprints.soton.ac.uk/416905/1/GE_Enterprise_vs_Product_Logic_final_v3_.docx }}</ref> and resulted in the outright cancellations of a number of orders placed for it. By 1967 these problems were cleared up, and the machines were re-launched along with an upgraded version of the [[GECOS]] [[operating system]].

A follow-on project to create a next-generation 635 started in 1967. The new '''GE-655''' replaced the individual [[transistor]]s from the earlier models with [[integrated circuit]]s, which doubled the performance of the machine while also greatly reducing assembly costs. However, the machine was still in development in 1969, and was announced but probably never delivered under that name.

By that time the Multics project had finally produced an operating system usable by end-users. Besides MIT, Bell Labs, and GE, GE-645 systems running Multics were installed at the [[US Air Force]] [[Rome Air Development Center|Rome Development Center]], [[Honeywell]] Billerica, and Machines Bull in Paris.  These last two systems were used as a "software factory" by a Honeywell/Bull project to design the Honeywell Level 64 computer.

GE sold its computer division to [[Honeywell]] in 1970, who renamed the GE-600 series as the [[Honeywell 6000 series]]. The 655 was officially released in 1973 as the '''Honeywell 6070''' (with reduced performance versions, the 6030 and 6050). An optional Decimal/Business instruction set was added to improve [[COBOL]] performance. This was the Extended Instruction Set, also known as EIS, and the Decimal Unit or DU. The machines with EIS were the 'even' series, the 6040, 6060, 6080 and later the 6025. Several hundred of these processors were sold. Memory was initially 600&nbsp;ns ferrite core made by Lockheed. Later versions used 750&nbsp;ns MOS memory. The two could co-exist within a system, but not within a memory controller.

A version of the 6080 with the various Multics-related changes similar to the 645 was released as the '''6180'''. A few dozen 6180-architecture CPUs were shipped. Later members of the 6000 series were released under various names, including Level 66, Level 68, DPS-8, DPS-88, DPS-90, DPS-9000 by Honeywell, [[Groupe Bull]], and [[NEC]].