PDP-8/L restoration blog.

Making a Posibus Peripheral Emulator

The PDP-8/L is a less expensive and much smaller version of the PDP-8/I. The PDP-8/I cost $12,000 and the PDP-8/L cost $8,000. Both were available from 1968 through 1971. The PDP-8/I backplane is wired for many common peripheral controllers and for 8K of core memory. The smaller PDP-8/L chassis only contains room for 4K of core, a paper tape reader (PR8/L) and punch (PP8/L) controller, data break facility, and the Teletype interface. The internal data break facility could only be used with a single controller for peripherals like a disk or tape. An expansion chassis (BA08) was available that provided an additional 4K of core (MC8/L). Controller boards for a Card Reader, Multiple Teletype, Storage Tube Display, Real-Time Clock, Oscilloscope Display, and Incremental Plotter could be added to the BA08 chassis. Additional peripherals like disk and tape drives could be connected to the system with Posibus cables.

As of 1/2/12 this system is running!

A total of 22 modules of the 100+ modules needed to be replaced.

Now we need to hunt for some peripherals.

By popular demand...

We left the original patina and cartoon on the front panel of the PDP-8/L. The toggle switch was replaced with a key switch when we replaced the power supply. The examine plastic toggle replaced was replaced with one donated by Ulrich N Fierz.