[Rhode Island Computer Museum Online]

RICM Online Computer Crypt - DEC PDP-10, S/N 4657 

[IMAGE - DEC PDP-10]

On April 23-24, 1999, in a cooperative effort, The Rhode Island Computer Museum and the Retro-Computing Society of Rhode Island placed in preservation the last commercially operating Digital Equipment Corporation DECSYSTEM 2020 (KS-10) computers in the New England area.

Approximately 20 years old, these machines were finally powered down on Thursday, the 21st. On Friday, crews dismantled the cabling and prepared individual pieces for shipment. On Saturday, the 23rd, the equipment was taken from its fourth floor location at the Strategic Planning Institute in Cambridge, MA and loaded onto two trucks for transport. On the 24th, the computers were off-loaded into temporary storage.

RCS/RI received some of the spare disk drive sets and one system is held by a private enthusiast in New Hampshire. A second system will be privately preserved, but hosted by RICM along with its own system. Eventually, these two systems will be restored to a working configuration, perhaps with Internet access.

Special thanks must to be accorded to Megan Gentry, who led the recovery team and coordinated the tri-state rescue effort; and the other participants, Carl Friend, Allison Parent, Chris Tucker, Merle Peirce, Richard Maliska, Don Mastrovito, Alla Andreyava, K. Ramm, Rich Grosz, Devon McCullough and Bob Houk.

As one participant said, "This has been a chance for me to actually see and touch equipment that I had only read about."


The KS10 is the smallest in the PDP10 family of 36 bit computers manufactured by Digital Equipment Corporation. It was introduced in 1978 as a small low cost version of the KL10. It has 512 Words of Cache Memory and supports a maximum of 512 Kwords (36-bit) of memory.

This machine has 512 KWords of RAM memory, a TU77 Tape Drive, a RP06 Disk Drive, 32 serial ports and a Line Printer interface.

The KS10 chassis in the 2020 contains the following boards:

Slot# Module# Option Description KS10 Chassis
1 M8629 MMA 64KW RAM
2 M8629 MMA 64KW RAM
3 M8629 MMA 64KW RAM
4 M8629 MMA 64KW RAM
5 M8629 MMA 64KW RAM
6 M8629 MMA 64KW RAM
7 M8629 MMA 64KW RAM
8 M8629 MMA 64KW RAM
9 M8618 MMC Memory Controller
10 Empty
11 M8623 CRM Micro Controller
12 M8622 CRA Micro Controller
13 M8620 DPE Data Path
14 M8621 DPM Data Path
15 Empty
16 M8619 UBA#3 Unibus Adapter
17 Empty
18 M8616 CSL Console
19 M8619 UBA#1 Unibus Adapter
20 Empty
21AB M9014 RH11 UNIBUS to 3 H854s
21CD M7297 RH11 MASSBUS parity control
21EF M7296 RH11 MASSBUS control and status
22 M7295 RH11 MASSBUS bus control
23 M7294YA RH11 MASSBUS data buffer and control
24CD M5904 RH11 MASSBUS control transceiver
24EF M688 RH11 UNIBUS power fail driver
25CD M5904 RH11 MASSBUS control transceiver
25EF M688 RH11 UNIBUS power fail driver
26CD M5904 RH11 MASSBUS control transceiver
27CD MG727 Unibus Grant
28AB M9300 UNIBUS terminator
28CD MG727 Unibus Grant
29AB M9300 UNIBUS terminator
29CD MG727 Unibus Grant

The Unibus chassis in the 2020 contains the following boards:

Slot# Module# Option Description
1      M9014    RH11    UNIBUS to 3 H854s e
2
3
4
5      M7819    DZ11-A  8-line double-buffered
   async EIA with modem control
6      M7819    DZ11-A  8-line double-buffered
   async EIA with modem control
7      M7819    DZ11-A  8-line double-buffered
   async EIA with modem control
8      M7819    DZ11-A  8-line double-buffered
   async EIA with modem control
9U     M9202         Unibus Jumper
9M     MG727         Grant
10
11U    M9202         Unibus Jumper
11M    M7297    RH11 MASSBUS parity control
11L    M7296    RH11 MASSBUS control and status
12     M7295    RH11 MASSBUS bus control
13     M7294YA  RH11 MASSBUS data buffer and ctl.
14M    M5904    RH11 MASSBUS control transceiver
14L    M688     RH11 UNIBUS power fail driver
15M    M5904    RH11 MASSBUS control transceiver
16M    M5904    RH11 MASSBUS control transceiver
17M    MG727         Grant
18U    M9300         UNIBUS terminator
18M    MG727         Grant
19U    M9202         Unibus Jumper
19M    MG727         Grant
20
21U    M9202         Unibus Jumper
21
22     M8586    LP20 LP20 control
23     M8571    LP20 ?
24U    M9300         UNIBUS terminator
24M    M8585    LP20 ?

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This page was last modified on Thursday, February 14, 2002.