Digital DF32 diskfile

UvA Computer Museum catalogue nr 96.39

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The DF32 Disk File and Control is a fixed disk storage device which was used with the PDP-8 (#96.17) in our collection. It has a capacity of 32768 13-bits words. The disk itself is heavy, 0.25 inch thick and nickel-cobalt plated. There are 16 data tracks, each with its own fixed read/write head; these heads are visible in four of the five units in the picture of the opened disk assembly. A fifth unit contains the heads corresponding to the four tracks reserved for timing and address information. On the edge of the disk is a reflective spot indicating the beginning of the various tracks.
The disk and r/w heads are enclosed by a removable dust cover. The manual gives instructions how to clean the disk if necessary. Also it recommends to connect the drive to an uninterruptible power supply, to avoid the wear caused by the r/w heads landing on the disk surface. (This author, having worked with a PDP-9 with a similar disk device, recalls that every time the power was interrupted for any reason, the Digital service technician had days of work before the system could be brought up again).

The picture shows the DF32 unit. The disk unit proper is at the left, standing on four legs with shock-absorbing feet (not visible). At the right is the controller/power supply section with a few switches, normally hidden behind a front panel. One of these switches is for processor selection (PDP-8, PDP-8/I or PDP-8/S). Up to four disk units could be served by a single controller and power supply.

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The Disk File was used with the BOL project at the IKO institute for nuclear physics, Amsterdam