Burroughs B1700
Encyclopedia
The Burroughs B1000 Series of computer
s consisted of three major generations which were the B1700, B1800, and B1900 series machines originally introduced in the 1970s and continued later on.
Much original research for the B1700, initially codenamed the PLP ("Proper Language Processor" or "Program Language Processor") was done at the Burroughs Pasadena
plant.
Production of the B1700s began in the mid 1970s and occurred at both the Santa Barbara
and Liege, Belgium plants. The majority of design work was done at Santa Barbara with the B1830 being the notable exception designed at Liege.
allowing the machine to emulate any other machine. The Burroughs MCP (Master Control Program) would schedule a particular job to run. The MCP would preload the interpreter
for whatever language was required. These interpreters presented different virtual machine
s for COBOL
, Fortran
, etc.
A notable idea of the "semantic gap" between the ideal expression of the solution to a particular programming problem, and the real physical hardware illustrated the inefficiency of current machine implementations. The three Burroughs architectures represent solving this problem by building hardware aligned with high-level languages. The large systems were stack machine
s and very efficiently executed ALGOL
. The medium systems (B2000, 3000, and B4000) were aimed at the business world and executing COBOL (thus everything was done with BCD
including addressing memory.) The B1000 series was perhaps the only "universal" solution from this perspective because it used idealized virtual machine
s for any language.
The actual hardware was built to enhance this capability. Perhaps the most obvious examples were the bit-addressable memory, the variable size arithmetic logic unit
(ALU), and the ability to OR in data from a register into the instruction register allowing very efficient instruction parsing. Another feature of the machine language was the appearance of having the output of the ALU appear as different addressable registers. X+Y, and X-Y are two read-only registers within the machine language.
arithmetic in the ALU
.
Internally the machines employed 16-bit
instructions and a 24-bit
data path. The bit addressable memory supported the mix quite efficiently. Internally, the later generation memories stored data on 32-bit
boundaries, but were capable of reading across this boundary and supplying a merged result.
The initial hardware implementations were built out of the CTL
Family originally made by Fairchild Semiconductor
but with the introduction of the B1955 in 1979 the series employed the more popular (and more readily obtainable) TTL
logic family. Up through the B1955, the control logic was implemented with PROMs
, muxes and such.
The B1965, the last of the series, was implemented with a pair of microcode
sequencers which stayed in lock step with each other. The majority of the instructions executed in a single cycle. This first cycle was decoded by FPLAs
using 16 inputs (just the perfect size for a 16-bit instruction word) and 48 min-terms. Successive cycles from a multi-cycle instruction were sourced from PROMs. The FPLAs and PROM outputs were wired together. The FPLA would drive the output on the first cycle, then get tri-stated. The PROMs would drive the control lines until the completion of the instruction.
Later models of the machines in both the 1800 and 1900 series could be configured as either a single or dual processor. These were tightly coupled machines and competed in access to the main memory. The B1955 and B1965 could accommodate up to four processors on the memory bus, but at least one of these would be assigned to the Multi-Line adapter which supplied serial I/O to the system. Only Dual-processor configurations were ever actually sold.
The Multi-Line was capable of driving multiple 19.2Kb RS485 serial lines in a multi-drop configuration. The serial I/O was polled. A given terminal would wait until it was addressed, and grab the line and send any data it had pending.
The Multi-Line Adapter would DMA
the data into main memory in a linked list
format. Consequently, the processors didn't have to deal with serial I/O interrupt issues. This was taken care of by the fact that block mode terminals were the only type supported.
The B1000 series could address a maximum of 2 megabyte
s of memory. In these days of multiple gigabyte
s that sounds fairly limiting, but most commercial installations got by with hundreds of kilobyte
s of storage.
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s consisted of three major generations which were the B1700, B1800, and B1900 series machines originally introduced in the 1970s and continued later on.
Much original research for the B1700, initially codenamed the PLP ("Proper Language Processor" or "Program Language Processor") was done at the Burroughs Pasadena
Pasadena, California
Pasadena is a city in Los Angeles County, California, United States. Although famous for hosting the annual Rose Bowl football game and Tournament of Roses Parade, Pasadena is the home to many scientific and cultural institutions, including the California Institute of Technology , the Jet...
plant.
Production of the B1700s began in the mid 1970s and occurred at both the Santa Barbara
Santa Barbara, California
Santa Barbara is the county seat of Santa Barbara County, California, United States. Situated on an east-west trending section of coastline, the longest such section on the West Coast of the United States, the city lies between the steeply-rising Santa Ynez Mountains and the Pacific Ocean...
and Liege, Belgium plants. The majority of design work was done at Santa Barbara with the B1830 being the notable exception designed at Liege.
Writeable control store
The B1000 is distinguished from other machines in that it had a writeable control storeControl store
A control store is the part of a CPU's control unit that stores the CPU's microprogram. It is usually accessed by a microsequencer. Early control stores were implemented as a diode-array accessed via address decoders, a form of read-only memory. This tradition dates back to the program timing...
allowing the machine to emulate any other machine. The Burroughs MCP (Master Control Program) would schedule a particular job to run. The MCP would preload the interpreter
Interpreter (computing)
In computer science, an interpreter normally means a computer program that executes, i.e. performs, instructions written in a programming language...
for whatever language was required. These interpreters presented different virtual machine
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
s for COBOL
COBOL
COBOL is one of the oldest programming languages. Its name is an acronym for COmmon Business-Oriented Language, defining its primary domain in business, finance, and administrative systems for companies and governments....
, Fortran
Fortran
Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
, etc.
A notable idea of the "semantic gap" between the ideal expression of the solution to a particular programming problem, and the real physical hardware illustrated the inefficiency of current machine implementations. The three Burroughs architectures represent solving this problem by building hardware aligned with high-level languages. The large systems were stack machine
Stack machine
A stack machine may be* A real or emulated computer that evaluates each sub-expression of a program statement via a pushdown data stack and uses a reverse Polish notation instruction set....
s and very efficiently executed ALGOL
ALGOL
ALGOL is a family of imperative computer programming languages originally developed in the mid 1950s which greatly influenced many other languages and became the de facto way algorithms were described in textbooks and academic works for almost the next 30 years...
. The medium systems (B2000, 3000, and B4000) were aimed at the business world and executing COBOL (thus everything was done with BCD
BCD
BCD may refer to:* Binary coded decimal, representation of individual decimal digits in binary.* Bad Conduct Discharge, a form of discharge from US military service* Barrels per calendar day, a unit for measuring output of oil refineries...
including addressing memory.) The B1000 series was perhaps the only "universal" solution from this perspective because it used idealized virtual machine
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
s for any language.
The actual hardware was built to enhance this capability. Perhaps the most obvious examples were the bit-addressable memory, the variable size arithmetic logic unit
Arithmetic logic unit
In computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations.The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...
(ALU), and the ability to OR in data from a register into the instruction register allowing very efficient instruction parsing. Another feature of the machine language was the appearance of having the output of the ALU appear as different addressable registers. X+Y, and X-Y are two read-only registers within the machine language.
Internals
One concession to the fact that Burroughs was primarily a supplier to business (and thus running COBOL) was the availability of BCDBinary-coded decimal
In computing and electronic systems, binary-coded decimal is a digital encoding method for numbers using decimal notation, with each decimal digit represented by its own binary sequence. In BCD, a numeral is usually represented by four bits which, in general, represent the decimal range 0 through 9...
arithmetic in the ALU
ALU
ALU, alu or Alu may refer to:*Academy of Fine Arts and Design, Ljubljana*Assisted Living Unit, care residency that usually includes the regular provision of a range of personal services*Alcatel-Lucent, a company traded on the NYSE...
.
Internally the machines employed 16-bit
16-bit
-16-bit architecture:The HP BPC, introduced in 1975, was the world's first 16-bit microprocessor. Prominent 16-bit processors include the PDP-11, Intel 8086, Intel 80286 and the WDC 65C816. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16...
instructions and a 24-bit
24-bit
Notable 24-bit machines include the ICT 1900 series and the Harris H series.The IBM System/360, announced in 1964, was a popular computer system with 24-bit addressing and 32-bit general registers and arithmetic...
data path. The bit addressable memory supported the mix quite efficiently. Internally, the later generation memories stored data on 32-bit
32-bit
The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....
boundaries, but were capable of reading across this boundary and supplying a merged result.
The initial hardware implementations were built out of the CTL
CTL
CTL can refer to:*Computation tree logic*Cut-to-length logging*Complex Text Layout languages*cytotoxic T cell *Commission de transport de la Ville de Laval...
Family originally made by Fairchild Semiconductor
Fairchild Semiconductor
Fairchild Semiconductor International, Inc. is an American semiconductor company based in San Jose, California. Founded in 1957, it was a pioneer in transistor and integrated circuit manufacturing...
but with the introduction of the B1955 in 1979 the series employed the more popular (and more readily obtainable) TTL
Transistor-transistor logic
Transistor–transistor logic is a class of digital circuits built from bipolar junction transistors and resistors. It is called transistor–transistor logic because both the logic gating function and the amplifying function are performed by transistors .TTL is notable for being a widespread...
logic family. Up through the B1955, the control logic was implemented with PROMs
Programmable read-only memory
A programmable read-only memory or field programmable read-only memory or one-time programmable non-volatile memory is a form of digital memory where the setting of each bit is locked by a fuse or antifuse. Such PROMs are used to store programs permanently...
, muxes and such.
The B1965, the last of the series, was implemented with a pair of microcode
Microcode
Microcode is a layer of hardware-level instructions and/or data structures involved in the implementation of higher level machine code instructions in many computers and other processors; it resides in special high-speed memory and translates machine instructions into sequences of detailed...
sequencers which stayed in lock step with each other. The majority of the instructions executed in a single cycle. This first cycle was decoded by FPLAs
Field-programmable gate array
A field-programmable gate array is an integrated circuit designed to be configured by the customer or designer after manufacturing—hence "field-programmable"...
using 16 inputs (just the perfect size for a 16-bit instruction word) and 48 min-terms. Successive cycles from a multi-cycle instruction were sourced from PROMs. The FPLAs and PROM outputs were wired together. The FPLA would drive the output on the first cycle, then get tri-stated. The PROMs would drive the control lines until the completion of the instruction.
I/O
The I/O system for the B1000 series consisted of a 24 bit data path and control strobes to and from the peripherals. The CPU would place data on the data path, then inform the peripheral that data was present. Many of the peripheral adapters were fairly simplistic, and the CPU actually drove the adapter state machines through their operations with successive accesses.Later models of the machines in both the 1800 and 1900 series could be configured as either a single or dual processor. These were tightly coupled machines and competed in access to the main memory. The B1955 and B1965 could accommodate up to four processors on the memory bus, but at least one of these would be assigned to the Multi-Line adapter which supplied serial I/O to the system. Only Dual-processor configurations were ever actually sold.
The Multi-Line was capable of driving multiple 19.2Kb RS485 serial lines in a multi-drop configuration. The serial I/O was polled. A given terminal would wait until it was addressed, and grab the line and send any data it had pending.
The Multi-Line Adapter would DMA
DMA
DMA can refer to:* DMA , a defunct dance music magazine* Dallas Museum of Art, an art museum in Texas, USA* Danish Music Awards, an award show held in Denmark since 1989...
the data into main memory in a linked list
Linked list
In computer science, a linked list is a data structure consisting of a group of nodes which together represent a sequence. Under the simplest form, each node is composed of a datum and a reference to the next node in the sequence; more complex variants add additional links...
format. Consequently, the processors didn't have to deal with serial I/O interrupt issues. This was taken care of by the fact that block mode terminals were the only type supported.
The B1000 series could address a maximum of 2 megabyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
s of memory. In these days of multiple gigabyte
Gigabyte
The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means 109 in the International System of Units , therefore 1 gigabyte is...
s that sounds fairly limiting, but most commercial installations got by with hundreds of kilobyte
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
s of storage.