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The PDP-10 was a mainframe computer[1] manufactured by Digital Equipment Corporation (DEC) from the late 1960s on; the name stands for "Programmed Data Processor model 10". Mainframes (often colloquially referred to as Big Iron) are Computers used mainly by large organizations for critical applications typically bulk data Digital Equipment Corporation was a pioneering American company in the Computer industry It was the machine that made time-sharing common; it looms large in hacker folklore because of its adoption in the 1970s by many university computing facilities and research labs, the most notable of which were MIT's AI Lab and Project MAC, Stanford's SAIL, Computer Center Corporation (CCC), and Carnegie Mellon University. Time-sharing refers to sharing a computing resource among many users by multitasking. Project MAC (the MIT Project on Mathematics and Computation later the MIT Laboratory for Computer Science ( LCS) was a research laboratory at MIT Leland Stanford Junior University, commonly known as Stanford University or simply Stanford, is a private Research university located in The Stanford Artificial Intelligence Laboratory (also known as Stanford AI Lab or SAIL) is the Artificial intelligence (AI research laboratory of Carnegie Mellon University (also known as CMU) is a private Research University in Pittsburgh, Pennsylvania, United

The PDP-10 architecture was an almost identical version of the earlier PDP-6 architecture, sharing the same 36-bit word length and slightly extending the instruction set (but with improved hardware implementation). The PDP-6 ( P rogrammed D ata P rocessor- 6) was a Computer model developed by Digital Equipment Corporation (DEC Many early computers aimed at the scientific market had a 36- Bit word length. Some aspects of the instruction set are unique, most notably the "byte" instructions, which operated on arbitrary sized bit-fields (at that time a byte was not necessarily eight bits). An instruction set is a list of all the instructions and all their variations that a processor can execute A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science.

Contents

Models and technical evolution

KA10 Flip Chip containing 9 transistors, 1971
KA10 Flip Chip containing 9 transistors, 1971

The original PDP-10 processor was the KA10, introduced in 1968. It used discrete transistors packaged in DEC's Flip-Chip® technology, with backplanes wire wrapped via a semi-automated manufacturing process. In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals Flip-Chip modules were used in the DEC PDP-7 (Referred to in documentation as the "FLIP CHIP" PDP-8, PDP-9 and PDP-10 This article deals with electronics manufacturing and prototyping techniques see Wire wrap jewellery for the Jewellery related topic Abisolierwerkzeug In 1973, the KA10 was replaced by the KI10, which used TTL SSI. Transistor–transistor logic ( TTL) is a class of Digital circuits built from Bipolar junction transistors (BJT and Resistors It is called Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside This was joined in 1975 by the higher-performance KL10 (later the KL20), which was built from ECL, was microprogrammed, and had cache memory. In electronics emitter-coupled logic, or ECL, is a Logic family in which current is steered through bipolar transistors to implement Logic Microprogramming (ie writing microcode) is a method that can be employed to implement Machine instructions in a CPU relatively easily often using less A smaller, less expensive model, the KS10, was introduced in 1978, using TTL and Am2901 bit-slice components and including the PDP-11 Unibus to connect peripherals. Bit slicing is a technique for constructing a processor from modules of smaller bit width The PDP-11 was a series of 16-bit Minicomputers sold by Digital Equipment Corp The Unibus was the earliest of several bus technologies used with PDP-11 and early VAX systems manufactured by the Digital Equipment Corporation

The KA10 had a maximum main memory capacity (both virtual and physical) of 256 kilowords (equivalent to 1152 kilobytes). In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two A kilobyte (derived from the SI prefix Kilo -, meaning 1000 is a unit of Information or Computer storage equal to either 1024 As supplied by DEC, it did not include paging hardware; memory management consisted of two sets of protection and relocation registers, called "base and bounds" registers. In Computer Operating systems that have their Main memory divided into pages, paging (sometimes called swapping) is a transfer This allowed each half of a user's address space to be limited to a set section of main memory, designated by the base physical address and size. In Computing, an address space defines a range of discrete addresses each of which may correspond to a physical or virtual Memory register, a network host Computer data storage, often called storage or memory, refers to Computer components devices and recording media that retain digital This allowed the model (later used by Unix) of separate read-only shareable code segment (normally the high segment) and read-write data/stack segment (normally the low segment). Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer Read-write memory is a type of Computer memory that may be relatively easily written to as well as read from In Computer science, a stack is an Abstract data type and Data structure based on the principle of Last In First Out (LIFO Some KA10 machines (e. g. first at MIT, and later at BBN) were modified to add support for paging, as well as more physical memory.

The KI10 and later processors offered paged memory management, and also supported a larger physical address space of 4 megawords. In Computing, " word " is a term for the natural unit of data used by a particular computer design

KL10 Wire-Wrap CPU Backplane
KL10 Wire-Wrap CPU Backplane

The original KL10 models (1070, 1080, etc. ) used the original PDP-10 memory bus, with external memory modules. The processors used in the DECSYSTEM-20 (2040, 2050, 2060, 2065), commonly but incorrectly called "KL20", used internal memory, mounted in the same cabinet as the CPU. The DECSYSTEM-20 was a 36-bit DEC PDP-10 Computer running the TOPS-20 operating system The 10xx models 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 differences between the 10xx and 20xx models were more cosmetic than real; some 10xx systems had "20-style" internal memory and I/O, and some 20xx systems had "10-style" external memory and an I/O bus. In particular, all ARPAnet TOPS-20 systems had an I/O bus because the AN20 IMP interface was an I/O bus device. Both could run either TOPS-10 or TOPS-20 microcode and thus the corresponding operating system.

KL10-DA 1090 CPU and Memory
KL10-DA 1090 CPU and Memory

The I/O architecture of the 20xx series KL machines was based on a new DEC bus design called the MASSbus. While many attributed the success of the PDP-11 to DEC's decision to make the PDP-11 Unibus an open architecture, DEC reverted to prior philosophy with the KL, making MASSbus both unique and proprietary. Consequently, there were no aftermarket peripheral manufacturers who made devices for the MASSbus, and DEC chose to price their own MASSbus devices, notably the RP06 disk drive, at a substantial premium above comparable IBM-compatible devices. CompuServe for one, designed its own alternative disk controller that could operate on the MASSbus, but connect to IBM style 3330 disk subsystems.

Later, the "Model B" version of the 2060 processors removed the 256 kiloword limitation on the virtual address space, by allowing the use of up to 32 "sections" of up to 256 kilowords each, along with substantial changes to the instruction set. In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two In Computing, " word " is a term for the natural unit of data used by a particular computer design "Model A" and "Model B" KL10 processors can be thought of as being different CPUs. The first operating system that took advantage of the Model B's capabilities was TOPS-20 release 3, and user mode extended addressing was offered in TOPS-20 release 4. TOPS-20 versions after release 4. 1 would only run on a Model B.

The KS10 design was crippled to be a Model A even though most of the necessary data paths needed to support the Model B architecture were present. This was no doubt intended to segment the market, but it greatly shortened the KS10's product life. A market segment is a subgroup of people or organizations sharing one or more characteristics that cause them to have similar product needs

The final upgrade to the KL10 was the MCA25 upgrade of a 2060 to 2065, which gave some performance increases for programs which run in multiple sections.

Instruction set architecture

From the first PDP-6's to the Model A KL-10's, the user-mode instruction set architecture was largely the same. An instruction set is a list of all the instructions and all their variations that a processor can execute This section covers that architecture.

Addressing

The PDP-10 has 36-bit words and 18-bit word addresses. In supervisor mode, instruction addresses correspond directly to physical memory. In user mode, addresses are translated to physical memory. Earlier models gave a user process a "high" and a "low" memory: addresses with a 0 top bit used one base register, and higher addresses used another. Each segment was contiguous. Later architectures had paged memory access, allowing non-contiguous address spaces. The registers can also be addressed as memory locations 0-15.

Registers

There are 16 general-purpose, 36-bit registers. The right half of these registers (other than register 0) is used for indexing. A few instructions operate on pairs of registers. There is also a condition register, which records extra bits from the results of arithmetic operations (e. g. overflow), and can only be accessed by a few instructions.

Supervisor mode

There are two operational modes, supervisor and user mode. Besides the difference in memory referencing described above, supervisor-mode programs can execute input/output operations.

Communication from user-mode to supervisor-mode is done through Unimplemented User Operations (UUOs): instructions which are not defined by the hardware are trapped by the supervisor. This mechanism is also used both to emulate operations which may not have hardware implementations in cheaper models.

Data types

The major datatypes which are directly supported by the architecture are two's complement 36-bit integer arithmetic (including bitwise operations), 36-bit floating-point, and halfwords. The two's complement of a Binary number is defined as the value obtained by subtracting the number from a large power of two (specifically from 2 N for Extended, 72-bit, floating point is supported through special instructions designed to be used in multi-instruction sequences. Byte pointers are supported by special instructions. A word consisting of a "count" half and a "pointer" half supports bounded regions of memory, notably stacks.

Instructions

The instruction set is very symmetric. Every instruction consists of a 9-bit opcode, a 4-bit register code, and a 23-bit effective address field, which consists in turn of a 1-bit indirect bit, a 4-bit register code, and an 18-bit offset. Instruction execution begins by calculating the effective address. It adds the contents of the given register (if non-zero) to the offset, then if the indirect bit is 1, fetches the word at the calculated address and repeats the effective address calculation (possibly indefinitely, but will in fact terminate with a trap after 32 iterations). The resulting effective address can be used by the instruction either to fetch memory contents, or simply as a constant. Thus, for example, MOVEI A,3(C) adds 3 to the 18 lower bits of register C and puts the result in register A, without touching memory.

There are three main classes of instruction: arithmetic, logical, and move; conditional jump; conditional skip (which may have side effects); and several smaller classes.

The arithmetic, logical, and move operations include variants which operate immediate-to-register, memory-to-register, register-to-memory, and register-and-memory-to-both or memory-to-memory. Since registers act like part of memory, register-to-register operations are also defined. (Not all variants are useful, though they are well-defined. ) For example, the ADD operation has as variants ADDI (add an 18-bit Immediate constant to a register), ADDM (add register contents to Memory), ADDB (add to Both, that is, add register contents to memory and also put the result in the register). A more elaborate example is HLROM (Half Left to Right Ones to Memory), which takes the Left half of the register contents, places them in the Right half of the memory location, and replaces the left half of the memory location with Ones.

The conditional jump operations examine register contents and jump to a given location depending on the result of the comparison. For example, JUMPN A,LOC jumps to LOC if A is non-zero. There are also conditional jumps based on the processor's condition register.

The conditional skip operations compare register and memory contents and skip the next instruction (which is often an unconditional jump) depending on the result of the comparison. A simple example is CAMN A,LOC which compares the contents of register A with the contents of location LOC and skips the next instruction if they are not equal. A more elaborate example is TLCE A,LOC (read "Test Left Complement, Skip if equal"), which using the contents of LOC as a mask, selects the corresponding bits in the left half of register A. If all those bits are Equal to zero, skip the next instruction; and in any case, replace those bits by their boolean complement.

Some smaller instruction classes include the shift/rotate instructions and the procedure call instructions. Particularly notable are the stack instructions PUSH and POP and the corresponding stack call instructions PUSHJ and POPJ. The byte instructions use a special format of indirect word to extract and store arbitrary-sized bit fields, possibly advancing the pointer to the next unit.

Software

The original PDP-10 operating system was simply called "Monitor", but was later renamed to TOPS-10, at which time the system became known as the DECsystem-10. An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination The TOPS-10 System was a computer Operating system from Digital Equipment Corporation (DEC for the PDP-10 released in 1964, the resulting systems Early versions of Monitor and TOPS-10 formed the basis of Stanford's WAITS operating system and the Compuserve time-sharing system. WAITS was a heavily-modified variant of Digital Equipment Corporation 's Monitor Operating system (later renamed to and better known as TOPS-10) for the CompuServe, ( CompuServe Information Service, also known by its acronym CIS) was the first major commercial Online service in the United States

Over time, some PDP-10 operators began running operating systems assembled from major components developed outside DEC. For example, the main Scheduler might come from one university, the Disk Service from another, and so on. The commercial timesharing services such as CompuServe, Online Systems, and Rapidata maintained sophisticated inhouse systems programming groups so that they could modify the operating system as needed for their own businesses without being dependent on DEC or others. CompuServe, ( CompuServe Information Service, also known by its acronym CIS) was the first major commercial Online service in the United States In some ways, this was one of the first open source environments, although the commercial operators tended to only take code from open sources, keeping their own proprietary enhancements to themselves.

BBN developed their own alternative operating system, TENEX, which fairly quickly became the de facto standard in the research community. The TOPS-20 Operating system by Digital Equipment Corporation (DEC was the second proprietary OS for the PDP-10. DEC later ported Tenex to the KL10, enhanced it considerably, and named it TOPS-20, forming the DECSYSTEM-20 line. The TOPS-20 Operating system by Digital Equipment Corporation (DEC was the second proprietary OS for the PDP-10. MIT also had developed their own influential system, ITS (named in parody of the CTSS operating system). 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

Tymshare developed TYMCOM-X, derived from TOPS-10 but using a page-based file system like TOPS-20. Tymnet was an international data communications network headquartered in San Jose, California that utilized virtual call packet switched technology and used X The TOPS-10 System was a computer Operating system from Digital Equipment Corporation (DEC for the PDP-10 released in 1964, the resulting systems The TOPS-20 Operating system by Digital Equipment Corporation (DEC was the second proprietary OS for the PDP-10.

Clones

In the 1970s, researchers at Xerox PARC, frustrated by top company management's refusal to let them purchase a PDP-10 (Xerox had just bought SDS, and wanted PARC to use an SDS machine), designed and constructed two clone systems named "MAXC" (pronounced "Max", in honour of Max Palevsky, who had sold SDS to Xerox) for their own use; they ran a modified version of TENEX. PARC (Palo Alto Research Center Inc formerly Xerox PARC, is a Research and development company in Palo Alto California that began as a division of Scientific Data Systems, or SDS, was an American Computer company founded in September 1961 by Max Palevsky, a veteran of Packard Bell Max Palevsky (born 1924 in Chicago Illinois) is an American art collector venture capitalist philanthropist and computer technology pioneer

Third-party attempts to sell PDP-10 clones were relatively unsuccessful; see Foonly, Systems Concepts, and XKL. Foonly was the Computer company formed by Dave Poole, who was one of the principal Super Foonly designers as well as one of hackerdom s more colorful Systems Concepts (now the SC Group is a company co-founded by Stewart Nelson and Mike Levitt focused on making hardware products related to the

Cancellation and influence

The PDP-10 was eventually eclipsed by the VAX supermini machines (descendants of the PDP-11) when DEC recognized that the PDP-10 and VAX product lines were competing with each other and decided to concentrate its software development effort on the more profitable VAX. Name "VAX" was originally an Acronym for V irtual A ddress e' X' tension, both because the VAX was seen as a 32-bit The PDP-11 was a series of 16-bit Minicomputers sold by Digital Equipment Corp The PDP-10 product line cancellation was announced in 1983, including cancelling the on-going Jupiter project to produce a new high-end PDP-10 processor (despite that project being in good shape at the time of the cancellation). The Jupiter project was to be a successor to Digital Equipment Corporation (DEC 's PDP-10 model

This event spelled the doom of ITS and the technical cultures that had spawned the original jargon file, but by the 1990s it had become something of a badge of honor among old-time hackers to have cut one's teeth on a PDP-10. 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 The Jargon File is a Glossary of hacker Slang. The original Jargon File was a collection of hacker slang from technical cultures such as the MIT AI

The PDP-10 assembly language instructions LDB and DPB (load/deposit byte) live on as functions in the programming language Common Lisp. See the terminology section below for information regarding inconsistent use of the terms assembly and assembler A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. A programming language is an Artificial language that can be used to write programs which control the behavior of a machine particularly a Computer. Common Lisp, commonly abbreviated CL, is a dialect of the Lisp Programming language, published in ANSI standard document Information See the "notes" section on the LISP article — the 36-bit word size of the PDP-6 and PDP-10 was influenced by the programming convenience of having 2 LISP pointers, each 18 bits, in one word. Lisp (or LISP) is a family of Computer Programming languages with a long history and a distinctive fully parenthesized syntax

Will Crowther created Adventure, the prototypical computer adventure game, for a PDP-10. William ("Willie" or "Will" Crowther (born 1936 is a Computer programmer and caver. Colossal Cave Adventure (also known as ADVENT, Colossal Cave, or Adventure) (Crowther 1976 Crowther Don Daglow created the first computer baseball game (1971) and Dungeon (1975), the first computer role playing game (RPG) on a PDP-10. Don Daglow (born circa 1953 is an American Computer game and Video game designer, programmer and producer. Baseball is a Bat-and-ball Sport played between two teams of nine players each A computer role-playing game ( CRPG) is a broad Video game genre originally developed for personal computers and other home computers Walter Bright originally created Empire for the PDP-10. Walter Bright is a Computer programmer known for being the designer of the D programming language. Roy Trubshaw and Richard Bartle created the first MUD on a PDP-10. Roy Trubshaw (1959 -) was a Programmer at the University of Essex who co-authored with Richard Bartle, the first known MUD on a DEC Richard Allan Bartle (born January 10, 1960, in England) is a British writer and game researcher best known for being the co-author of In computer gaming, a MUD ( Multi-User Dungeon, Domain or Dimension) is a multi-player computer game that combines elements of In addition, Zork was written on the PDP-10, and Infocom used several PDP-10s for game development and testing. Zork was one of the first Interactive fiction Computer games and an early descendant of Colossal Cave Adventure. Infocom was a Software company, based in Cambridge Massachusetts, that produced numerous works of Interactive fiction.

Trivia

Some of the CGI for the Disney science fiction movie TRON was rendered on the Foonly F-1 PDP-10 clone. Computer animation Computer-generated imagery (also known as CGI) is the application of the field of Computer graphics or more specifically 3D computer graphics Tron is a 1982 Disney Science fiction film starring Jeff Bridges as Kevin Flynn (and his counterpart inside the electronic world Foonly was the Computer company formed by Dave Poole, who was one of the principal Super Foonly designers as well as one of hackerdom s more colorful It is also noteworthy that the PDP-10 has a TRON instruction (Test Right-halfword Ones and skip if Not masked) with the opcode 666 (octal). In computer technology an opcode ( op eration code) is the portion of a Machine language instruction that specifies the operation to be performed Coincidentally, former PDP-10 programmers created the Intellivision TRON video games that followed the release of the film. The Intellivision is a Video game console released by Mattel in 1979.

One of the largest collections of DECsystem-10 architecture systems ever assembled was at CompuServe, which at its peak operated over 200 loosely-coupled systems in three data centers in Columbus, Ohio. CompuServe, ( CompuServe Information Service, also known by its acronym CIS) was the first major commercial Online service in the United States Columbus is the Capital and the largest city of the US state of Ohio. CompuServe used these systems as 'hosts', providing access to commercial applications as well as the CompuServe Information Service. While the first such systems were purchased from DEC, when DEC abandoned the PDP-10 architecture in favor the VAX, CompuServe and other PDP-10 customers began purchasing plug-compatible computers from Systems Concepts. Name "VAX" was originally an Acronym for V irtual A ddress e' X' tension, both because the VAX was seen as a 32-bit As of January 2007, CompuServe continues to operate a small number of PDP-10 architecture machines to perform some billing and routing functions.

The main power supplies used in the KL-series machines was so inefficient that CompuServe engineers designed a replacement power supply that consumed about half the energy. CompuServe offered to license the design for its KL power supply to DEC for free if DEC would promise that any new KL purchased by CompuServe would have the more efficient power supply installed. DEC declined the offer.

Another modification made to the PDP-10 by CompuServe engineers was the replacement of the hundreds of incandescent indicator lamps on the KI-10 processor cabinet with LED lamp modules. The cost of the conversion was easily offset by the cost savings in electric consumption, the reduction of heat, and the manpower required to replaced burned-out lamps. There were no similar banks of indicator lamps on KL and KS processors.

The KL class machines could not be started without the assist of a PDP-11/40 frontend computer installed in every system. The PDP-11 was booted from a dual-ported RP06 disk drive (or alternatively from an 8" floppy disk drive or DECtape), and then commands could be given to the PDP-11 to start the main processor, which was typically booted from the same RP06 disk drive as the PDP-11. A floppy disk is an increasingly Obsolete data storage medium that is composed of a disk of thin flexible ("floppy" Magnetic storage medium encased DECtape, originally called Microtape was a Magnetic tape data storage medium used with many Digital Equipment Corporation Computers including the The PDP-11 would perform watchdog functions once the main processor was running.

The KS system used a similar boot procedure. An 8080 CPU loaded the microcode from an RM03 or RP06 disk or magnetic tape and the started the main processor. The 8080 switched modes after the operating system booted and controlled the console and remote diagnostic serial ports.

Systems Concepts built a demonstration model of laptop computer version of the PDP-10. It is not known whether this unit still exists.

In the movie Swordfish, Stanley the hacker stores the code for his worm on a PDP-10 in a file room of Caltech that was kept online, and on the internet, for "historical sake"

With the initial success of the VAX, DEC-10 engineers claimed that this stood for "Virtually A Ten(X)"

The 2Fort map for Team Fortress 2 features a pair of PDP-10 machines, RED team has a red painted system, whereas BLU team naturally has a blue machine. Swordfish is a 2001 action / thriller Film. It was directed by Dominic Sena and stars Hugh Jackman This would imply that BLU have a DECSystem-10 running TOPS-10 and RED have a DECSYSTEM-20 running TOPS-20.

This article is based in part on the Jargon File, which is in the public domain. The Jargon File is a Glossary of hacker Slang. The original Jargon File was a collection of hacker slang from technical cultures such as the MIT AI

See also

Further reading

References

  1. ^ Ceruzzi, Paul E. (2003). A History of Modern Computing. MIT Press, 208. ISBN 0262532034.  "It was large—even DEC's own literature called it [PDP-10] a mainframe. "

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Paul Gardner Allen (born January 21 1953 is an American computer programmer and entrepreneur who co-founded Microsoft with Bill Gates. Digital Equipment Corporation was a pioneering American company in the Computer industry
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