IBM 7094 Hardware Modifications for CTSS (RPQs)


The IBM 7090 and 7094 computers used for CTSS were modified with four non-standard hardware features, known as "RPQs", special order items for which the purchaser was instructed to "Request Price Quotation". A fifth RPQ, used to attach non-IBM equipment, was installed on the Project Mac 7094.

  1. IBM RPQ E07291 (PDF), Multiprogramming Package

    Undated revision #3 of IBM's formal description of the RPQ. Provided relocation and protection modes and registers. Not copyrighted.

    Two MIT Computation Center memoranda described how this RPQ worked and was to be used. They were scanned from a set of spirit duplicator (Ditto machine) paper copies.

    CC-189-1 (PDF): Latest Write-up on M.I.T. 7090 RPQ for Relocation and Protection Modes, March 1963, by Marjorie Merwin Daggett (replaces an earlier version ca. December 1961). The document consists of a cover page, followed by four numbered pages that are apparently Eugene Annunziata's original 1961 memo specifying the protection and relocation RPQ. Following the four numbered pages is an unnumbered page of errata. The handwritten notes on the four numbered pages are the corrections indicated in the errata.

    CC-209 (PDF): Use of the Memory Protection and Relocation Mode within the MOD.10 Time-Sharing System, May 1963, by R. C. Daley and F. J. Corbató.
  2. IBM RPQ E02120 (PDF), Additional Core Storage

    April 1963 revision #1 of IBM's formal description of the RPQ. Provided a second bank of 32,768 36-bit words of magnetic core memory. © 1961 expired 1989 without being renewed.

  3. IBM RPQ F02120 (PDF), Core Storage Clock and Interval Timer

    November 1960 revision #1 of IBM's formal description of the RPQ. Location 5 in core memory was incremented 60 times/second and caused a trap on overflow. This feature may also have been documented as IBM Engineering Instruction 570220 but it has not been verified. © 1960 expired 1988 without being renewed.

  4. Trap Feature for the IBM 7289 Drum Channel, IBM RPQ unknown

    As originally delivered the drum channel did not have the ability to signal an end-of-operation interrupt, so MIT immediately requested design and implementation of such a feature. It is not known whether IBM assigned a formal RPQ number, since the only documentation so far located is in IBM Engineering Instruction 572526 (PDF), a two-page appendix attached to the IBM Functional Specifications for the 7289 drum channel (PDF) (March, 1964).

  5. IBM RPQ M90976 (PDF), Direct Data Connection for IBM 7090

    Original issue circa 1960 of IBM's formal description of the RPQ including detailed specifications. This RPQ was installed on an IBM 7607 Data Channel to allow connection of a non-IBM device. It was apparently used on Channel D of the Project MAC 7094 to connect the Electronic Systems Laboratory graphic display that was informally called the Kludge. © 1960 expired 1988 without being renewed.

Preservation Credits: RPQs E07291, E02120, and F89349 provided by EI 572526 and RPQ 90976 provided by David Pitt. CC-189-1 and CC-209 were scanned by Roger Roach and Olin Sibert as part of the Multics History Project.

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