Jump to content

IBM 700/7000 series

From Wikipedia, the free encyclopedia
This is an old revision of this page, as edited by ArnoldReinhold (talk | contribs) at 23:01, 27 July 2004 (add commercial and decimal architecture details). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

The IBM 700/7000 series was a series of incompatible large scale (mainframe) computer systems made by IBM through the 1950s and early 1960s. They were made obsolete by the introduction of the System/360 (announcend in 1964).

Architectures

The IBM 700/7000 series had four completely different ways of storing data and instructions:

  • Scientific (36/18-bit words): 701 (Defense Calculator)
  • Scientific (36-bit words): 704, 709, 7090, 7094, 7040, 7044
  • Commercial (variable length character strings): 702, 705, 7080, 7010
  • Decimal (10 digit words): 7070, 7074
  • Supercomputer (64-bit words): 7030 "Stretch"

The 700 class used vacuum tubes, the 7000 class was transistorized. While the architectures differed, the machines in the same class shared electronics technologies and generally used the same peripherals (tape drives, card readers, card punches. Early peripherals were based on IBM accounting machine technology and even had wiring boards. Later peripherals were adopted from the IBM 1401 midline series.

Early computers were sold without software. As operating systems began to emerge, having four different mainframe architectures plus the 1401 midline architectures became a major problem for IBM since it meant at least four different programming efforts were required.

The System/360 combined the best features of the 7000 and 1401 series architectures into a single design, however the larger 360's had optional features that allowed them to emulate the 1400 and 7000 instruction sets in microcode. One of the selling points of the System/370 was improved 1400/7000 series emulation (it could be done under operating system control instead of shutting down and restarting in emulation mode as was done on the 360s).

Earliest Architecture - 701 only

Data Formats

Numbers were either 36 bits or 18 bits long, only fixed point.

Instruction Format

Instructions were 18 bits long, single address.

Registers

  • AC  - 38-bit Accumulator
  • MQ - 36-bit Multiplier-Quotient

Memory

2,048 or 4,096 – 36-bit binary words with six-bit characters

Scientific Architecture

Data Formats

Numbers were 36 bits long, both fixed point and floating point.

Instruction Format

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 (seven in the 7094) index registers, 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.

Registers

  • AC  - 38-bit Accumulator
  • MQ - 36-bit Multiplier-Quotient
  • XR  - 15-bit Index Registers (three or seven)
  • SI    - 36-bit Sense Indicator

The Accumulator (and Multiplier-Quotient) registers operated in signed magnitude format.

The Index registers operated using two's complement format and when used to modify an instruction address were subtracted from the address in the instruction. On machines with three index registers, if the tag had 2 or 3 bits set (i.e. selected multiple registers) then their values were ORed together before being subtracted. The IBM 7094, with seven index registers had a "compatibility" mode to permit programs from earlier machines that used this trick to continue to be used.

The Sense Indicators permitted interaction with the operator via panel switches and lights.

Memory

32,768 – 36-bit binary words with six-bit characters

Commercial Architecture (705)

Data format

Data was represented by a variable length string of characters terminated by a Record mark.

Registers

  • Accumulator - 256 characters
  • one auxiliary storage unit - 32 characters
  • 14 auxiliary storage units - 16 characters

Memory

  • 20,000 characters (core memory)
  • Character cycle rate - 17 microseconds

The 700/7000 commercial architecture also spawned the very successful IBM 1400 series (IBM 1401, IBM 1410, IBM 1440, IBM 1460) of mid-sized business computers.

Decimal Architecture

Data format

  • Word length - 10 decimal digit plus sign
  • Digit encoding - 2 out of 5

Registers

  • All registers one word, could also be addressed as memory
  • Accumulators - 3 (addresses 9991, 9992, and 9993)
  • Program counter - 1 (address 9995)
  • Index registers - 99 (addresses 0001-0099)

Memory

  • 5000 to 9900 words - core memory
  • Add time - 72 microseconds (7070)
  • Floating point - optional. Two digit exponent.

Instruction format

  • All instructions one word
  • 2 digit op code (including sign)
  • 2 digit index register
  • 2 digit field control
  • 4 digit address


IBM 700 series, vacuum tubes, 1950s

IBM 7000 series, transistors, 1960s

External links:

Retrieved from "https://en.wikipedia.org/w/index.php?title=IBM_700/7000_series&oldid=4880486"