Digital Equipment Corporation
LINC-8 Laboratory Computer

[JPEG image of LINC-8]

    Introduced in 1966, the LINC-8 is a hybrid between the original "straight" PDP-8 and the LINC (or Laboratory INstrumentation Computer). Only 142 were ever produced; this is serial number 10. The machine was withdrawn from manufacture in 1969.

    Following the stunning production run of 50 (remember - this was the early '60s) of the original LINC, Digital decided to manufacture a machine that embodied the exemplary laboratory interfaces of the LINC and the general data- processing abilities of the PDP-8. This is the result and was introduced just a year following the debut of the PDP-8 in 1965. The LINC-8 was the predecessor of the PDP-12 which was introduced in 1969 following the LINC-8's discontinuance.

    [JPEG image of LINC-8 logic bay] The PDP-8 portion of the LINC-8 is an exact copy of the "straight" -8, but with a few modifications to allow it to interface with, and control, the LINC processor which functions as a -8 peripheral. The standard memory in the system was 4 kW of core memory. The logic resides on a swing- out rear door with the memory and interface circuitry in the top third, the LINC processor in the middle third, and the PDP-8 in the bottom. The logic is all R-, S-, B-, and G- Flip Chips with a heavy preponderance of R- series modules. There's also a smattering of A- series A/D modules and some W- series cable connectors. The photograph here shows the LINC, most of the PDP-8, and a little bit of the memory and I/O logic frames.

    As previously mentioned, the LINC processor functions as an I/O peripheral to the PDP-8 for its "front panel" functions and as a Data- Break device for its memory accesses. When the LINC is in operation, the PDP-8 is held in a locked Break state and is effectively halted. The PDP-8 is responsible for controlling all aspects of LINC operation, setup, and most of the LINC's I/O must pass through the -8. This task is handled by a special PDP-8 program known as "PROGOFOP" (PROGram OF OPeration) which, when running, allows the machine's operator to exercise LINC functions from the front panel.

    The LINC-8 has a dual front panel in that all the functions for both machines are readily accessible from switches on the console. There are also lights (incandescent) which display the current status of both processors simultaneously. From a "cold start" (i.e. with empty memory), only the PDP-8 controls have any function (with the exception of the LINC "LOAD" toggle). Once PROGOFOP is loaded and is "listening" for LINC switch activations, the LINC processor becomes active. The LOAD switch initiates a boot function which accesses the LINCtape drive and loads PROGOFOP automatically.

    The standard range of peripherals offered with the LINC-8 was very suitable for laboratory work and the machines were popular for use in the medical milieu. The machine offered, off the shelf, a small oscilloscope, a Teletype ASR-33 , six relay outputs, and 8 digital- to- analogue conversion channels. Eight more D/A channels were reserved for comparison levels and were controlled by 8 potentiometers located on either side of the CRT.

    A dual- transport LINCtape drive was also standard with this device. LINCtape is a block- addressable format which uses a 1- inch wide tape sectored out into 256 word (1/4 kW) blocks. Each of these blocks could be addressed randomly, like a floppy. This was the direct precursor of DECtape. For more information about LINCtape, see the LINCtape section of my online version of the PDP-12 Users' Handbook . Note that the LINCtape drives on this machine are the original LINCtape devices, not TU-55s as in the case of the -12.

    The LINC-8 here appears by arrangement with the Retro- Computing Society of Rhode Island .

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