DECSYSTEM-20

The DECSYSTEM-20 was a 36-bit Digital Equipment Corporation PDP-10 mainframe computer running the TOPS-20 operating system.

PDP-10 computers running the TOPS-10 operating system were labeled DECsystem-10 as a way of differentiating them from the PDP-11. Later on, those systems running TOPS-20 (on the KL10 PDP-10 processors) were labeled DECSYSTEM-20 (the block capitals being the result of a lawsuit brought against DEC by Singer, which once made a computer called "system-10"). The DECSYSTEM-20 was sometimes called PDP-20, although this designation was never used by DEC.

The following models were produced:

• DECSYSTEM-2020: bit-slice processor with up to 512 kilowords of solid state RAM (The ADP OnSite version of the DECSYSTEM-2020 supported 1 MW of RAM)
• DECSYSTEM-2040: ECL processor with up to 1024 kilowords of magnetic core RAM
• DECSYSTEM-2050: ECL processor with 2K words of cache and up to 1024 kilowords of RAM
• DECSYSTEM-2060: ECL processor with 2k words of cache and up to 4096 kilowords of solid state memory
• DECSYSTEM-2065: DECSYSTEM-2060 with MCA25 pager (double-sized (1024 entry) 2-way associative hardware page table)

The only significant difference the user could see between a DECsystem-10 and a DECSYSTEM-20 was the operating system and the color of the paint. Most (but not all) machines sold to run TOPS-10 were painted "Blasi Blue",^[1] whereas most TOPS-20 machines were painted "Terracotta" (often mistakenly called "Chinese Red" or orange; the actual name of the color on the paint cans was Terracotta^[1]).

There were some significant internal differences between the earlier KL10 Model A processors, used in the earlier DECsystem-10's running on KL10 processors, and the later KL10 Model Bs, used for the DECSYSTEM-20s. Model As used the original PDP-10 memory bus, with external memory modules. The later Model B processors used in the DECSYSTEM-20 used internal memory, mounted in the same cabinet as the CPU. The Model As also had different packaging; they came in the original tall PDP-10 cabinets, rather than the short ones used later on for the DECSYSTEM-20.

The last released implementation of DEC's 36-bit architecture was the single cabinet DECSYSTEM-2020, using a KS10 processor.

The DECSYSTEM-20 was primarily designed and used as a small mainframe for timesharing. That is, multiple users would concurrently log on to individual user accounts and share use of the main processor to compile and run applications. Separate disk allocations were maintained for all users by the operating system, and various levels of protection could be maintained by for System, Owner, Group and World users.

Remaining Machines

The Living Computer Museum of Seattle, Washington maintains a 2065 running TOPS-10, which is available to interested parties via telnet upon registration (at no cost) at their website.

References

• C. Gordon Bell, Alan Kotok, Thomas N. Hasting, Richard Hill, "The Evolution of the DECsystem-10", in C. Gordon Bell, J. Craig Mudge, John E. McNamara, Computer Engineering: A DEC View of Hardware Systems Design (Digital Equipment, Beford, 1979)
• Frank da Cruz, Christine Gianone, The DECSYSTEM-20 at Columbia University 1977-1988

1. ^ ^{a b} System Paint, Digital Equipment Corporation, 1998

This article is based in part on the Jargon File, which is in the public domain.

This mainframe computer-related article is a stub. You can help Wikipedia by expanding it.v · Categories: DEC hardware DEC mainframe computers Mainframe computer stubs Wikimedia Foundation. 2010. Игры ⚽ Нужно сделать НИР? PDP-10 Programmed Data Processor Look at other dictionaries: DECsystem — was a line of server computers from Digital Equipment Corporation. They were based on MIPS architecture processors and ran DEC s version of the UNIX operating system, called Ultrix. They ranged in size from workstation style desktop enclosures to …   Wikipedia DECSYSTEM-20 — Le DECSYSTEM 20 était un ordinateur DEC PDP 10 équipé du système d exploitation propriétaire TOPS 20[1]. Le DEC 20 était parfois appelé PDP 20, mais jamais par DEC. Notes et références ↑ (en) …   Wikipédia en Français PDP-10 — KL10 DA 1090 CPU and 6 Memory Modules The PDP 10 was a mainframe computer family[1] manufactured by Digital Equipment Corporation …   Wikipedia PDP-10 — El CPU KL10 DA 1090 y 6 módulos de memoria El PDP 10 fue un computador fabricado por Digital Equipment Corporation (DEC) desde finales de los años 1960 en adelante. El nombre significa Programmed Data Processor model 10 (Procesador de Datos… …   Wikipedia Español DECstation — The model identification medallion of a DECstation 5000 Model 120 …   Wikipedia Digital Equipment Corporation — Industry Computer manufacturing Fate Assets were sold to various companies. What remained was sold to Compaq. Successor …   Wikipedia DEC Radix-50 — RADIX 50, commonly called Rad 50 or RAD50, is a character encoding created by Digital Equipment Corporation for use on their DECsystem, PDP, and VAX computers. RADIX 50 s 40 character repertoire (050 in octal) allows up to 3 characters to be… …   Wikipedia TOPS-10 — Company / developer Digital Equipment Corporation Programmed in MACRO 10, BLISS OS family DEC OS family Working state Discontinued Latest stable release 7.04 …   Wikipedia Massbus — The Massbus was a high performance computer input/output bus designed in the 1970s by the Digital Equipment Corporation of Maynard, Massachusetts. The bus was used by Digital to interconnect its highest performance computers with magnetic disk… …   Wikipedia Alan Kotok — Infobox Scientist name = Alan Kotok image width = 260px caption = Kotok speaking in Boston in 2004. Photo: Richard Ishida birth date = birth date|1941|11|9|df=y birth place = Philadelphia, Pennsylvania death date = death date and… …   Wikipedia 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”