PDP 11/45 Further success! (and a question)

Jim Beacon jim at g1jbg.co.uk
Mon Mar 21 13:36:14 CST 2005

Hi All,

I replaced the UBC today (I found a serviceable spare of the same version in
our works stores, last tested 1994....), and I can now key in a program,
examine it and run it.

I now need to concentrate on the PSU, before I start putting the rest of the
cards back. I must also repair my UBC, in case work decides they want theirs
back (unlikely, but you can never tell with bean counters).

Now a question, I used the light flasher program:

location    contents    opcode
001000    012700        mov #1,r0
001002    000001
001004    006100        rol r0
001006    000005        reset
001010    000775        br -4

and it will run, however, I don't see the data lights "chase" across the
console. If I single step, the program performs as expected, with the data
lights going across the panel (data switch in "Data Paths" position). Also,
if I run the program and halt it, the light appear at a different data bit
depending on how long I let the program run (I can continue the program and
it will move to a different bitn at the next halt). Am I doing something
stupid, or are the bulbs just too slow to display the data? (I suppose it
could be a function of the power supply fault, but I don't think it would
manifest itself in this way).



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