Programming the PDP-6

The AI lab PDP-10 shared its memory and I/O buses with a PDP-6. The PDP-6 has 16K of core memory which the PDP-10 can also read and write. The PDP-6 can not see the PDP-10 memory. Both processors can send an interrupt to the other.

For ITS to talk to the PDP-6, the system location PDP6UP must first be set to -1. To access the PDP-6 core memory from ITS, create a job named “PDP6” or “PDP10”. (Historical side note. At first the roles were reversed: the PDP-6 was running ITS and the PDP-10 was the subordinate processor.) This job will have a 16K core image and reads and writes will go directly to the PDP-6 memory. DDT can load a program with $L. It's not possible to start, stop, or set breakpoints. These things will have to be done from the PDP-6 console.