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--- programming_the_pdp-6 [2020/03/18 06:56]
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+++ programming_the_pdp-6 [2020/03/18 14:59]
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 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.
-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.
+For ITS to talk to the PDP-6, the 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.