A computer component consisting of two rectangular printed circuit boards mounted one above the other. One is primarily green in colour, the other yellow. Along the lower edge of the green board are seven edge connectors, each with two rows of pins offset vertically. Running along the centre of the board is a captive fastener that is used to seat the board correctly within the KSR1 supercomputer. Turning the fastener with a special hex wrench closed a clamshell on the zero force connector that mounted the board to the mainframe chassis.
Note that this artifact belongs to the personal collection of Norman Wilson.
Accession Number: 2026.cs.7
Alternative Name: APRD cell, Processor board.
Primary Materials: Steel, Aluminum, Copper, Silicon.
Printed along the edge of green PCB: KENDALL SQUARE RESEARCH CORP. © 1991 MADE IN U.S.A P/N 3-204 REV 04″
Upper white label on edge of green PCB: “[barcode] SN 6173”
Lower white label on edge of green PCB: “[barcode] PN 1 – 1// REV 4 0”
Leftmost white label on upper edge of board: “PN 1-70 SN 6173”
Rightmost white label on upper edge of board: “PN 1-1 REV 40”
Upper white label on upper edge of yellow PCB: “[barcode] SN 6506”
Lower white label on upper edge of yellow PCB: “[barcode] PN 1 – 2// REV 0 5”
A note, handwritten by Norman Wilson on a notepad with OCLSC (Ontario Centre for Large Scale Computation) letterhead, reads as follows: “APRD 6173 BROKEN// Tried as spare 9 Jun 98// May have caused havoc// Confirmed bad 11 Jun — passes quick agenda, but KSR OS gets traps// when this cell is in system.”
Dimensions (cm): Height = 20.5, Width = 3, Length = 33.
This KSR1 APRD (Allcache Processor, Router, and Directory) board (or “cell”) is a replaceable, modular component of the KSR1 highly parallel computer. Each such board incorporates KSR’s proprietary Sharp-manufactured 64-bit CPU, 32 megabytes of memory, and the hardware required to communicate the other APRD cells in the system. This arrangement created a platform that could be expanded to a maximum of 34,816 MB, an arrangement that would have incorporated 1,088 such APRD cells. (The U of T installation used 32 cells.)
KSR computers used a shared-memory (“Allcache”) architecture, with each APRD unit having an equal proportion of the total system memory. Memory is allocated based on processor need and access patterns.
The board is in very good cosmetic condition and shows only very light wear. A note that accompanies the artifact indicates that it is faulty. (See “Markings” field.)
Associated Instruments:
Kendall Square Research, Cambridge, Massachusetts.
Date of Manufacture: 1991
This component was collected by Norman Wilson. As indicated by the accompanying note (see accompanying image and transcription in “Markings” field), this board was diagnosed as faulty in June of 1998.
Note that the OCLSC letterhead is anachronistic as that institution was closed in April of 1992. Norman Wilson, who had worked there in support of the Cray X-MP supercomputers, retained a number of the letterhead pads, which were “reasonably nice paper”.
Norman Wilson (part-time consulting systems administrator in the University of Toronto Department of Computer Science) Computer Science History Project interview with Erich Weidenhammer and John Dimarco, Toronto, Ontario, 25 June 2026.
Calvin C. Gotlieb, John W. Ross, Edmund West, and Norman Wilson (1994). “Acquiring and Running a Kendall Square Research KSR1” In Supercomputing Symposium ’94 : Proceedings : Canada’s Eighth Annual International High Performance Computing Conference and Exhibition, June 6-8, 1994, Toronto, Ontario, Canada. Edited by John W. Ross. The University of Toronto, 1994.
Kendall Square Research (1992). KSR1 Technology Background, January 1992. Digitized by Internet Archive.
Following the demise of the Ontario Centre for Large Scale Computation (OCLSC) and the removal of its Cray X-MP/24 supercomputer in April of 1992, the University of Toronto undertook an extensive process to acquire a parallel supercomputer. After soliciting proposals from a number of vendors, a selection process took place after which negotiations were opened with Kendall Square Research.
A purchase agreement was signed in July of 1993, and a new KSR1-32 was installed and running by September of 1993 (See Gotlieb et al 1994). The KSR1 was located in the same machine room on the top floor of the north wing of the McLennan Physical Laboratories building as the earlier Cray computers.
The Toronto KSR1 had 32 CPUs (i.e. APRD cells), 16 of which were (initially, at least) on loan from KSR. Responsibility for the system was assigned to University of Toronto Instructional and Research Computing (UTIRC), a department in the University of Toronto Division of Computation and Communications. This particular APRD board was diagnosed as faulty by sysadmin Norman Wilson in June of 1998.
In February 1994, Kendall Square Research went bankrupt. Having warned the U of T about the impending bankruptcy, a supply of spares was acquired to keep the computer running. Although the UTIRC was disbanded about a year after KSR’s bankruptcy, the machine was maintained in operation until around the year 2000.
Norman Wilson, who maintained the KSR1 over its time at the University of Toronto, praises its industrial design, noting that “… It was, for the most part, at least for routine things, one of the most pleasant systems to maintain that I’ve ever had my hands on” (Wilson interview, 2026).