The IBM 709 was a

computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...

system, initially announced by IBM 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 a large digital mainframe computer introduced by IBM in 1954. It was the first mass-produced computer with hardware for floating-point arithmetic. The IBM 704 ''Manual of operation'' states: The type 704 Electronic Data-Proce ...

, and was the third of the IBM 700/7000 series 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 of the Hindu–Arabic numeral ...

arithmetic, leading zero suppression, and several other operations. The 709 had 32,768 words of 36-bit

magnetic core memory Magnetic-core memory was the predominant form of random-access computer memory for 20 years between about 1955 and 1975. Such memory 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 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 software or use pe ...

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 first 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, 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 potential difference has been applied. The type known as ...

s. IBM announced a transistorized version of the 709, called the IBM 7090, 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 registers whose contents are subtracted from the base address instead of being added to it. All three index registers can participate in an instruction: the 3-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 is a logical connective typically notated as \lor and read aloud as "or". For instance, the English language sentence "it is raining or it is snowing" can be represented in logic using the disjunctive formula R \lor S ...

operation, not addition.IBM 709 Reference Manual, Form A22-6501-0, 1958^p. 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 that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can ...

numbers have a magnitude sign, an 8-bit excess-128 exponent and a 29-bit significand * 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 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 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 A boot is a type of footwear. Most boots mainly cover the foot and the ankle, while some also cover some part of the lower calf. Some boots extend up the leg, sometimes as far as the knee or even the hip. Most boots have a heel that is c ...

) from card, tape or drum. The IBM 738 Magnetic Core Storage used on 709 was also a milestone of hybrid technology. Although the core array drivers are all vacuum tube, the read sense amplifiers were a very early use of transistors in computing.

References

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

Registers

Instruction and data formats

I/O channel

See also

References

Further reading

External links