IBM 709
Encyclopedia
The IBM 709 was an early computer
system introduced by IBM in August, 1958. It was an improved version of the IBM 704
and the second member of the IBM 700/7000 series of scientific computers.
The IBM 709 added overlapped input/output, indirect addressing, and three "convert" instructions (which provided support for decimal
arithmetic, leading zero suppression, and several other operations). The 709 had 32,768 words of 36-bit memory and could execute 42,000 add or subtract instructions or 5000 multiplies per second.http://www.columbia.edu/acis/history/ibm709.html
An optional hardware emulator
executed legacy IBM 704 programs on the IBM 709. This was the first commercially available emulator prior to 1960. 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 709 was built using vacuum tube
s. IBM introduced a transistorized version of the 709, called the IBM 7090
, in November 1959.
The FORTRAN Assembly Program was first introduced for the 709.
whose contents were subtracted from the base address instead of being added to it. All three decrement registers could participate in an instruction: the 3 bit tag field in the instruction was a bit map specifying which of the registers would participate in the operation.
Type A instructions had, in sequence, a three bit prefix (instruction code), a 15 bit decrement field, a 3 bit tag field, and a 15 bit address field. They were conditional jump operations based on the values in the decrement registers specified in the tag field. Some also subtracted the decrement field from the contents of the decrement registers. The implementation required 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 had, in sequence, a 12 bit instruction code (with the second and third bits set to 0 to distinguish them from type A instructions), a two bit flag field, four unused bits, a 3 bit tag field, and a 15 bit address field.
The instruction set implicitly subdivided the data format into the same fields as type A instructions: prefix, decrement, tag and address. Instructions existed to modify each of these fields in a data word without changing the remainder of the word.
The IBM-738 Magnetic Core Storage used on the 709 was also a milestone of hybrid technology. Although the core array drivers were all vacuum tube, the read sense amplifiers were a very early use of transistors in computing.
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...
system introduced by IBM in August, 1958. It was an improved version of the IBM 704
IBM 704
The IBM 704, the first mass-produced computer with floating point arithmetic hardware, was introduced by IBM in 1954. The 704 was significantly improved over the IBM 701 in terms of architecture as well as implementations which were not compatible with its predecessor.Changes from the 701 included...
and the second member of the IBM 700/7000 series of scientific computers.
The IBM 709 added overlapped input/output, indirect addressing, and three "convert" instructions (which provided support for decimal
Decimal
The decimal numeral system has ten as its base. It is the numerical base most widely used by modern civilizations....
arithmetic, leading zero suppression, and several other operations). The 709 had 32,768 words of 36-bit memory and could execute 42,000 add or subtract instructions or 5000 multiplies per second.http://www.columbia.edu/acis/history/ibm709.html
An optional hardware emulator
Emulator
In computing, an emulator is hardware or software or both that duplicates the functions of a first computer system in a different second computer system, so that the behavior of the second system closely resembles the behavior of the first system...
executed legacy IBM 704 programs on the IBM 709. This was the first commercially available emulator prior to 1960. 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 709 was built using vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s. IBM introduced a transistorized version of the 709, called the IBM 7090
IBM 7090
The IBM 7090 was a second-generation transistorized version of the earlier IBM 709 vacuum tube mainframe computers and was designed for "large-scale scientific and technological applications". The 7090 was the third member of the IBM 700/7000 series scientific computers. The first 7090 installation...
, in November 1959.
The FORTRAN Assembly Program was first introduced for the 709.
Registers
The IBM 709 had a 38 bit accumulator, a 36 bit multiplier quotient register, and three 15 bit decrement registers. The decrement registers were a kind of index registerIndex register
An index registerCommonly known as a B-line in early British computers. in a computer's CPU is a processor register used for modifying operand addresses during the run of a program, typically for doing vector/array operations...
whose contents were subtracted from the base address instead of being added to it. All three decrement registers could participate in an instruction: the 3 bit tag field in the instruction was a bit map specifying which of the registers would participate in the operation.
Instruction and data formats
There were two instruction formats, referred to as "Type A" and "Type B". Most instructions were of type B.Type A instructions had, in sequence, a three bit prefix (instruction code), a 15 bit decrement field, a 3 bit tag field, and a 15 bit address field. They were conditional jump operations based on the values in the decrement registers specified in the tag field. Some also subtracted the decrement field from the contents of the decrement registers. The implementation required 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 had, in sequence, a 12 bit instruction code (with the second and third bits set to 0 to distinguish them from type A instructions), a two bit flag field, four unused bits, a 3 bit tag field, and a 15 bit address field.
- Fixed point numbers were stored in binary sign/magnitude formatComputer numbering formatsA computer number format is the internal representation of numeric values in digital computer and calculator hardware and software.-Bits:The concept of a bit can be understood as a value of either 1 or 0, on or off, yes or no, true or false, or encoded by a switch or toggle of some kind...
. - Single precision floating pointFloating pointIn computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...
numbers had a magnitude sign, an 8-bit excess-128 exponent and a 29 bit magnitude - Alphanumeric characters were 6-bit BCD, packed six to a word.
The instruction set implicitly subdivided the data format into the same fields as type A instructions: prefix, decrement, tag and address. Instructions existed 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 was a programmed function of the central processor - data words were transferred to or from the I/O register, one at a time, using a "copy" instruction - the 709 came with the IBM-766 Data Synchronizer, which provided two independently "programmed" I/O channels. Up to three Data Synchronizers could be attached to a 709, each able to control up to 20 tape drives and a card-reader/punch/printer set. This allowed six times as many I/O devices on the 709, and allowed I/O to proceed on multiple devices while program execution continued in parallel.The IBM-738 Magnetic Core Storage used on the 709 was also a milestone of hybrid technology. Although the core array drivers were all vacuum tube, the read sense amplifiers were a very early use of transistors in computing.
External links
- 709 Data Processing System IBM history
- IBM 709 Data Processing System BRL report, with photos
- IBM 709 page at Columbia University, with photos.