Information about Tops 20
The TOPS-20 operating system by DEC was the second proprietary OS for the PDP-10. It was preferred by most PDP-10 hackers over TOPS-10 (at least by those who were not ITS or WAITS partisans). TOPS-20 began in 1969 as Bolt, Beranek and Newman's TENEX operating system, using special paging hardware. The system is almost entirely unrelated to the similarly-named TOPS-10 but shipped with the PA1050 TOPS-10 Monitor Calls emulation facility which allowed most, but not all, TOPS-10 executables to run unchanged. As a matter of policy DEC did not update PA1050 to support later TOPS-10 additions except where required by DEC software.
In 1964 DEC announced the PDP-6. DEC was still heavily involved with MIT's AI Lab, and many feature requests from the LISP hackers were moved into this machine. BBN became interested in buying one for their AI work when they became available, but wanted DEC to add a hardware version of Murphy's pager directly into the system. With such an addition, every program on the system would have paging support invisibly, making it much easier to do any sort of programming on the machine. DEC was initially interested, but soon (1966) announced they were in fact dropping the PDP-6 and concentrating solely on their smaller 18-bit and new 16-bit lines. The PDP-6 was expensive and complex, and had not sold well for these reasons.
It wasn't long until it became clear that DEC was once again entering the 36-bit business with what would become the PDP-10. BBN started talks with DEC to get a paging subsystem in the new machine, then known by its CPU name, the KA-10. DEC was not terribly interested. One development of these talks was the inclusion of two dual memory areas, allowing all programs to be divided into a protected (exec in DEC-speak) and user side. Additionally, DEC was firm on keeping the cost of the machine as low as possible, including only 16k words of core and placing registers in RAM, resulting in a considerable performance hit.
BBN nevertheless went ahead with its purchase of several PDP-10s, and decided to build their own hardware pager. During this period a debate began on what operating system to run on the new machines. Strong arguments were made for the continued use of TOPS-10, in order to keep their existing software running with minimum effort. This would require a re-write of TOPS to support the paging system, and this seemed like a major problem. At the same time, TOPS did not support a number of features the developers wanted. In the end they decided to make a new system, but include an emulation library that would allow it to run existing TOPS-10 software with minor effort.
The new system, soon known as TENEX, also included a full virtual memory system -- that is, not only could programs access a full 262kwords of memory, every program could do so at the same time. The pager system would handle mapping as it would always, copying data to and from the backing store as needed. The only change needed was for the pager to be able to hold several sets of mappings between RAM and store, one for each program using the system. The pager also held access time information in order to tune performance. The resulting pager was fairly complex, filling a full-height 19" rackmount chassis.
One notable feature of TENEX was its user-oriented command line interpreter. Unlike typical systems of the era, TENEX deliberately used long command names and even included noise words to further expand the commands for clarity. For instance, Unix uses
TENEX became fairly popular in the small PDP-10 market, and the external pager hardware developed into a small business of its own. In early 1970 DEC started work on an upgrade to the PDP-10 processor, the KI-10. BBN once again attempted to get DEC to support a full hardware paging system, but instead DEC decided on a much simpler system. This plan eventually backfired; by this point TENEX was one of the most popular PDP-10 operating systems, and it would not run on the new machines. Known as the DECsystem-10 in the marketplace, the normal operating system was TOPS-10, which did not include any sort of virtual memory system.
Just as the new TENEX was shipping, DEC started work on the KL-10, intended to be a low-cost version of the KI-10. While this was going on, Stanford University AI-programmers, many of them MIT alumni, were working on their own project to build a PDP-10 that was ten times faster than the original KA-10's. DEC visited them and many of their ideas were then folded into the KL-10 project as well. The same year IBM also announced their own machine with virtual memory, making it a requirement for any computer. In the end the KL integrated a number of major changes to the system, and didn't end up being any lower cost. From the start, the new DECSYSTEM-20 would run a version of TENEX as its default operating system.
Extensions for the new machine were limited, but difficult. The main upgrade was the addition of extended addressing, which allowed the machine to support 23-bits of address. The extra bits were "added" by the pager hardware, which was now implemented in microcode. The extra bits of the address allowed multiple pages to be mapped into the same physical hardware, which also allowed the system to support a wider range of RAM without it being "obvious". For backward compatibility, the machine included instructions that could generate 18-bit addresses on demand.
The first in-house code name for the operating system was VIROS (VIRtual memory Operating System); when customers started asking questions, the name was changed to SNARK so DEC could truthfully deny that there was any project called VIROS. When the name SNARK became known, the name was briefly reversed to become KRANS; this was quickly abandoned when someone objected that "krans" meant "funeral wreath" in Swedish (though it simply means "wreath"; this part of the story may be apocryphal).
Ultimately DEC picked TOPS-20 as the name of the operating system, and it was as TOPS-20 that it was marketed. The hacker community, mindful of its origins, quickly dubbed it TWENEX (a contraction of "twenty TENEX"), even though by this point very little of the original TENEX code remained (analogously to the differences between AT&T V7 Unix and BSD). DEC people cringed when they heard "TWENEX", but the term caught on nevertheless (the written abbreviation "20x" was also used).
TWENEX was successful and very popular; in fact, there was a period in the early 1980s when it commanded as fervent a culture of partisans as Unix or ITS - but DEC's decision to scrap all the internal rivals to the VAX architecture and its VMS OS killed the DEC-20 and put an end to TWENEX's brief period of popularity. DEC attempted to convince TOPS-20 users to convert to VMS, but instead, by the late 1980s, most of the TOPS-20 hackers had migrated to Unix.
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TENEX
In the 1960's BBN was involved in a number of LISP-based artificial intelligence projects for DARPA, many of which had very large (for the era) memory requirements. One solution to this problem was to add paging software to the LISP language, allowing it to write out unused portions of memory to disk for later recall if needed. One such system had been developed for the PDP-1 at MIT by Dan Murphy before he joined BBN. Early DEC machines were based on an 18-bit word, allowing addresses to encode for a 262kword memory. The machines were based on expensive core memory and included nowhere near the required amount. The pager used the otherwise unused bits of the address to store a key into a table of blocks on a magnetic drum that acted as the pager's backing store, and the software would fetch the pages if needed and then re-write the address to point to the proper area of RAM.In 1964 DEC announced the PDP-6. DEC was still heavily involved with MIT's AI Lab, and many feature requests from the LISP hackers were moved into this machine. BBN became interested in buying one for their AI work when they became available, but wanted DEC to add a hardware version of Murphy's pager directly into the system. With such an addition, every program on the system would have paging support invisibly, making it much easier to do any sort of programming on the machine. DEC was initially interested, but soon (1966) announced they were in fact dropping the PDP-6 and concentrating solely on their smaller 18-bit and new 16-bit lines. The PDP-6 was expensive and complex, and had not sold well for these reasons.
It wasn't long until it became clear that DEC was once again entering the 36-bit business with what would become the PDP-10. BBN started talks with DEC to get a paging subsystem in the new machine, then known by its CPU name, the KA-10. DEC was not terribly interested. One development of these talks was the inclusion of two dual memory areas, allowing all programs to be divided into a protected (exec in DEC-speak) and user side. Additionally, DEC was firm on keeping the cost of the machine as low as possible, including only 16k words of core and placing registers in RAM, resulting in a considerable performance hit.
BBN nevertheless went ahead with its purchase of several PDP-10s, and decided to build their own hardware pager. During this period a debate began on what operating system to run on the new machines. Strong arguments were made for the continued use of TOPS-10, in order to keep their existing software running with minimum effort. This would require a re-write of TOPS to support the paging system, and this seemed like a major problem. At the same time, TOPS did not support a number of features the developers wanted. In the end they decided to make a new system, but include an emulation library that would allow it to run existing TOPS-10 software with minor effort.
The new system, soon known as TENEX, also included a full virtual memory system -- that is, not only could programs access a full 262kwords of memory, every program could do so at the same time. The pager system would handle mapping as it would always, copying data to and from the backing store as needed. The only change needed was for the pager to be able to hold several sets of mappings between RAM and store, one for each program using the system. The pager also held access time information in order to tune performance. The resulting pager was fairly complex, filling a full-height 19" rackmount chassis.
One notable feature of TENEX was its user-oriented command line interpreter. Unlike typical systems of the era, TENEX deliberately used long command names and even included noise words to further expand the commands for clarity. For instance, Unix uses
ls to print a list of files in a directory, whereas TENEX used DIRECTORY (OF FILES). "DIRECTORY" was the command word, "(OF FILES)" was noise added to make the purpose of the command clearer. Of course users didn't want to type these long commands, so TENEX used an escape recognition system that would expand out typing into commands. For instance, the user could type DIR and the escape key, at which point TENEX would replace the DIR with the full command. The same feature worked with file names, which took some effort on the part of the interpreter, and the system allowed for long file names with human-readable descriptions. TENEX also included a help system that could be invoked by typing the question mark, which would print out a list of possible matching commands and then return the user to the command line with the question mark removed.
TENEX became fairly popular in the small PDP-10 market, and the external pager hardware developed into a small business of its own. In early 1970 DEC started work on an upgrade to the PDP-10 processor, the KI-10. BBN once again attempted to get DEC to support a full hardware paging system, but instead DEC decided on a much simpler system. This plan eventually backfired; by this point TENEX was one of the most popular PDP-10 operating systems, and it would not run on the new machines. Known as the DECsystem-10 in the marketplace, the normal operating system was TOPS-10, which did not include any sort of virtual memory system.
TOPS-20
Learning from this mistake, the DEC sales manager in charge of the PDP-10 line managed to purchase the rights to TENEX from BBN and set up a project to port it to the new machine. At around this time Murphy moved from BBN to DEC as well, helping on the porting project. Most of the work centered on emulating the BBN pager hardware in a combination of software and the KI-10's simpler hardware. The speed of the KI-10 compared to the PDP-6 made this possible. Additionally the porting effort required a number of new device drivers to support the newer backing store devices being used.Just as the new TENEX was shipping, DEC started work on the KL-10, intended to be a low-cost version of the KI-10. While this was going on, Stanford University AI-programmers, many of them MIT alumni, were working on their own project to build a PDP-10 that was ten times faster than the original KA-10's. DEC visited them and many of their ideas were then folded into the KL-10 project as well. The same year IBM also announced their own machine with virtual memory, making it a requirement for any computer. In the end the KL integrated a number of major changes to the system, and didn't end up being any lower cost. From the start, the new DECSYSTEM-20 would run a version of TENEX as its default operating system.
Extensions for the new machine were limited, but difficult. The main upgrade was the addition of extended addressing, which allowed the machine to support 23-bits of address. The extra bits were "added" by the pager hardware, which was now implemented in microcode. The extra bits of the address allowed multiple pages to be mapped into the same physical hardware, which also allowed the system to support a wider range of RAM without it being "obvious". For backward compatibility, the machine included instructions that could generate 18-bit addresses on demand.
The first in-house code name for the operating system was VIROS (VIRtual memory Operating System); when customers started asking questions, the name was changed to SNARK so DEC could truthfully deny that there was any project called VIROS. When the name SNARK became known, the name was briefly reversed to become KRANS; this was quickly abandoned when someone objected that "krans" meant "funeral wreath" in Swedish (though it simply means "wreath"; this part of the story may be apocryphal).
Ultimately DEC picked TOPS-20 as the name of the operating system, and it was as TOPS-20 that it was marketed. The hacker community, mindful of its origins, quickly dubbed it TWENEX (a contraction of "twenty TENEX"), even though by this point very little of the original TENEX code remained (analogously to the differences between AT&T V7 Unix and BSD). DEC people cringed when they heard "TWENEX", but the term caught on nevertheless (the written abbreviation "20x" was also used).
TWENEX was successful and very popular; in fact, there was a period in the early 1980s when it commanded as fervent a culture of partisans as Unix or ITS - but DEC's decision to scrap all the internal rivals to the VAX architecture and its VMS OS killed the DEC-20 and put an end to TWENEX's brief period of popularity. DEC attempted to convince TOPS-20 users to convert to VMS, but instead, by the late 1980s, most of the TOPS-20 hackers had migrated to Unix.
Source
- Some text in this article was taken from The Jargon File entry on "TWENEX", which is in the public domain.
References
- Daniel G. Bobrow, Jerry D. Burchfiel, Daniel L. Murphy, Raymond S. Tomlinson, TENEX, A Paged Time Sharing System for the PDP-10 (Communications of the ACM, Vol. 15, pp. 135-143, March 1972)
External links
- Origins and Development of TOPS-20 is an excellent longer history
- Panda Programming TOPS-20 Home Page maintains a mailing list for TOPS-20 news
- SDF Public Access TWENEX
An operating system (OS) is the software that manages the sharing of the resources of a computer. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the
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Digital Equipment Corporation was a pioneering American company in the computer industry. It is often referred to within the computing industry as DEC. (This acronym was frequently officially used by Digital itself,[1] but the official name was always DIGITAL.
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The PDP-10 was a computer manufactured by Digital Equipment Corporation (DEC) from the late 1960s on; the name stands for "Programmed Data Processor model 10". It was the machine that made time-sharing common; it looms large in hacker folklore because of its adoption in the 1970s
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ITS, the Incompatible Timesharing System (named in comparison with the Compatible Time-Sharing System also in use at MIT), was an early, revolutionary, and influential MIT time-sharing operating system which was written in assembly; it was developed principally by the
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WAITS was a heavily modified variant of the Digital Equipment Corporation's Monitor operating system (later renamed to, and better known as TOPS-10) for the PDP-6 and PDP-10 mainframe computers, used at the Stanford Artificial Intelligence Laboratory (SAIL) up until 1990; the
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19th century - 20th century - 21st century
1930s 1940s 1950s - 1960s - 1970s 1980s 1990s
1966 1967 1968 - 1969 - 1970 1971 1972
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1930s 1940s 1950s - 1960s - 1970s 1980s 1990s
1966 1967 1968 - 1969 - 1970 1971 1972
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BBN Technologies (originally Bolt Beranek and Newman) is a high-technology company that provides research and development services. BBN is based next to Fresh Pond in Cambridge, Massachusetts, USA.
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General comments about TOPS-10
The TOPS-10 System was a computer operating system from Digital Equipment Corporation (DEC) for the PDP-10 released in 1964, the resulting systems being referred to as "DECsystem-10"[1]...... Click the link for more information.
Lisp
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ICD-9 307.9
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ICD-9 307.9
For the programming language, see .
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artificial intelligence (or AI) is "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions which maximizes its chances of success.
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Agency overview
Formed 1958
Employees 240
Annual Budget $3.2 billion
Agency Executive Anthony J. Tether, Director
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www.darpa.
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paging, sometimes called swapping, is a transfer of pages between main memory and an auxiliary store, such as hard disk drive.[1] Paging is an important part of virtual memory implemention in most contemporary general-purpose operating systems, allowing to easily
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Lisp
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ICD-10 F 80.8
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For the programming language, see .
A lisp (O E wlisp, stammering)[1] is a speech impediment, historically also known as ..... Click the link for more information.
PDP-1 (Programmed Data Processor-1) was the first computer in Digital Equipment Corporation's PDP series and was first produced in 1960. It is famous for being the computer most important in the creation of hacker culture, at MIT, BBN and
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Massachusetts Institute of Technology (MIT) is a private, coeducational research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing 32 academic departments,[3]
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Digital Equipment Corporation was a pioneering American company in the computer industry. It is often referred to within the computing industry as DEC. (This acronym was frequently officially used by Digital itself,[1] but the official name was always DIGITAL.
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Magnetic core memory, or ferrite-core memory, is an early form of computer memory. It uses small magnetic ceramic rings, the cores, to store information via the polarity of the magnetic field they contain.
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Drum memory was an early form of computer memory that was widely used in the 1950s and into the 1960s, invented by Gustav Tauschek in 1932 in Austria. For many machines, a drum
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Ram, ram, or RAM as a non-acronymic word
As a non-acronymic word Ram, ram, or RAM may refer to:Animals
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The PDP-6 (Programmed Data Processor-6) was a computer model developed by Digital Equipment Corporation (DEC) in 1963. It was influential primarily as the prototype (effectively) for the later PDP-10; the instruction sets of the two machines are
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The PDP-10 was a computer manufactured by Digital Equipment Corporation (DEC) from the late 1960s on; the name stands for "Programmed Data Processor model 10". It was the machine that made time-sharing common; it looms large in hacker folklore because of its adoption in the 1970s
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In computer architecture, a processor register is a small amount of storage available on the CPU whose contents can be accessed more quickly than storage available elsewhere.
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- This article is about the computer term. For the TBN game show, see Virtual Memory (game show).
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command line interpreter (also command line shell, command language interpreter) is a computer program that reads lines of text entered by a user and interprets them in the context of a given operating system or programming language.
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A device driver, or software driver is a computer program allowing higher-level computer programs to interact with a computer hardware device.
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A driver typically communicates with the device through the computer bus or communications subsystem to which the hardware is
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Leland Stanford Junior University, commonly known as Stanford University or simply Stanford, is a private university located approximately 37 miles (60 kilometers) southeast of San Francisco and approximately 20 miles (32 km) northwest of San Jose in Stanford,
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A microprogram implements a CPU instruction set. Just as a single high level language statement is compiled to a series of machine instructions (load, store, shift, etc), in a CPU using microcode, each machine instruction is in turn implemented by a series of microinstructions,
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In technology, especially computing (irrespective of platform), a product is said to be backward compatible (or downward compatible) when it is able to take the place of an older product, by interoperating with other products that were designed for the older product.
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AT&T Inc.
Public (NYSE: T )
Founded 1983[1]
Headquarters San Antonio, Texas, USA
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Public (NYSE: T )
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