IBM 709
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The IBM 709 is a
computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
system that was announced by
IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...
in January 1957 and first installed during August 1958. The 709 was an improved version of its predecessor, the
IBM 704 The IBM 704 is the model name of a large digital computer, digital mainframe computer introduced by IBM in 1954. Designed by John Backus and Gene Amdahl, it was the first mass-produced computer with hardware for floating-point arithmetic. The I ...
, and was the third of the
IBM 700/7000 series The IBM 700/7000 series is a series of large-scale (Mainframe computer, mainframe) computer systems that were made by IBM through the 1950s and early 1960s. The series includes several different, incompatible processor architectures. The 700s ...
of scientific computers. The improvements included overlapped input/output, indirect addressing, and three "convert" instructions which provided support for
decimal The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers (''decimal fractions'') of th ...
arithmetic, leading zero suppression, and several other operations. The 709 had 32,768 words of 36-bit
magnetic-core memory In computing, magnetic-core memory is a form of random-access memory. It predominated for roughly 20 years between 1955 and 1975, and is often just called core memory, or, informally, core. Core memory uses toroids (rings) of a hard magneti ...
and could execute 42,000 add or subtract instructions per second. It could multiply two 36-bit integers at a rate of 5000 per second. An optional hardware
emulator In computing, an emulator is Computer hardware, hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run sof ...
executed old IBM 704 programs on the IBM 709. This was the first commercially available emulator. Registers and most 704 instructions were emulated in 709 hardware. Complex 704 instructions such as floating-point trap and input-output routines were emulated in 709 software. The FORTRAN Assembly Program was introduced for the 709. It was a large system; customer installations used 100 to 250 kW to run them and almost as much again on the cooling. It weighed about (without peripheral equipment).IBM 709 Data Processing System
BRL report, (details of each installation) with photos
The 709 was built using
vacuum tube A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
s. IBM announced a transistorized version of the 709, called the
IBM 7090 The IBM 7090 is a second-generation Transistor computer, transistorized version of the earlier IBM 709 vacuum tube mainframe computer that was designed for "large-scale scientific and technological applications". The 7090 is the fourth member o ...
, in 1958, only a year after the announcement of the 709, thus cutting short the 709's product life.


Registers

The IBM 709 has a 38-bit accumulator, a 36-bit multiplier/quotient register, and three 15-bit
index register An index register in a computer's central processing unit, CPU is a processor register (or an assigned memory location) used for pointing to operand addresses during the run of a program. It is useful for stepping through String (computer science ...
s whose contents are subtracted from the base address instead of being added to it. All three index registers can participate in an instruction: the three-bit ''tag'' field in the instruction is a bit map specifying which of the registers participate in the operation, however if more than one index register is specified, their contents are combined by a
logical or In logic, disjunction (also known as logical disjunction, logical or, logical addition, or inclusive disjunction) is a logical connective typically notated as \lor and read aloud as "or". For instance, the English language, English language ...
operation, not addition.IBM 709 Reference Manual, Form A22-6501-0, 1958p. 12


Instruction and data formats

There are five instruction formats, referred to as Types A, B, C, D and E. Most instructions are of type B. Type A instructions have, in sequence, a 3-bit ''prefix'' (instruction code), a 15-bit ''decrement'' field, a 3-bit ''tag'' field, and a 15-bit ''address'' field. They are conditional jump operations based on the values in the decrement registers specified in the ''tag'' field. Some also subtract the ''decrement'' field from the contents of the index registers. The implementation requires that the second two bits of the instruction code be non-zero, giving a total of six possible type A instructions. One (STR, instruction code binary 101) was not implemented until the IBM 709. Type B instructions have, in sequence, a 12-bit instruction code (with the second and third bits set to 0 to distinguish them from type A instructions), a 2-bit ''flag'' field, four unused bits, a 3-bit ''tag'' field, and a 15-bit ''address'' field. Types C, D and E are used for specialized instructions. * Fixed-point numbers are stored in binary sign/magnitude format. * Single-precision
floating-point In computing, floating-point arithmetic (FP) is arithmetic on subsets of real numbers formed by a ''significand'' (a Sign (mathematics), signed sequence of a fixed number of digits in some Radix, base) multiplied by an integer power of that ba ...
numbers have a sign, an 8-bit excess-128 exponent and a 27-bit fraction (there was no "hidden bit"). * Alphanumeric characters are 6-bit BCD, packed six to a word. The instruction set implicitly subdivides the data format into the same fields as type A instructions: prefix, decrement, tag and address. Instructions exist to modify each of these fields in a data word without changing the remainder of the word.


I/O channel

The primary improvements of the 709 over the previous 704 involved more magnetic-core memory and apparently the first use of independent I/O channels. Whereas I/O on the 704 is a programmed function of the central processor - data words are transferred to or from the I/O register, one at a time, using a "copy" instruction - the 709 uses the IBM-766 data synchronizer, which provides two independently "programmed" I/O channels. Up to three Data Synchronizers can be attached to a 709, each able to control up to 20 IBM 729 tape drives and an IBM 716 alphanumeric line printer, IBM 711 card-reader and 721 card punch. This allows six times as many I/O devices on the 709, and allows I/O to proceed on multiple devices while program execution continues in parallel. Up to two IBM 733 Magnetic Drum units, each with 8,192 words of memory, could be attached independently from the Data Synchronizers. The 709 could initially load programs ( boot) from card, tape or drum. The IBM 738 Magnetic Core Storage used on the 709 was also a milestone of hybrid technology. Although the core array drivers all used vacuum tubes, the read sense amplifiers were a very early use of transistors in computing.


See also

* List of vacuum tube computers * IBM 740 CRT recorder * SHARE Operating System (SOS) * SQUOZE


References


Further reading

*


External links


709 Data Processing System
– IBM history

– BRL report, (details of each installation) with photos

– with photos {{IBM vacuum tube computers 709 7 0709 Computer-related introductions in 1958 36-bit computers