- IBM 709
The IBM 709 was an early
computer system introduced by IBM in August,1958 . It was an improved version of theIBM 704 and the second member of the IBM 700/7000 series of scientific computers. The IBM 709 added overlapped input/output,indirect address ing, and three "convert" instructions (which provided support fordecimal arithmetic, leading zero suppression, and several other operations).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 frequently used 704 instructions were emulated in 709 hardware. Complex 704 instructions were emulated in 709 software.The 709 was built using
vacuum tube s. IBM introduced a transistorized version of the 709, called theIBM 7090 , in November 1959.The
FORTRAN Assembly Program was first introduced for the 709.Instruction and data formats
The basic instruction format was a 3-bit "prefix", 15-bit "decrement", 3-bit "tag", and 15-bit "address". The prefix field specified the class of instruction. The decrement field often contained an immediate operand to modify the results of the operation, or was used to further define the instruction type. The three bits of the tag specified three "
index register s", the contents of which were "subtracted" from the address to produce an "effective address". The address field either contained an address or an immediate operand.*Fixed point numbers were stored in binary sign/magnitude format.
*Single precisionfloating point 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.External links
* [http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP709.html 709 Data Processing System] IBM history
* [http://ed-thelen.org/comp-hist/BRL61-ibm0709.html IBM 709 Data Processing System] BRL report with photos
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