Probs w. M3119 CXY08 MUX on VAX VMS 7.3

Paul Koning paulkoning at
Wed Aug 19 15:14:03 CDT 2015

> On Aug 19, 2015, at 3:33 PM, dave at wrote:
> From: Paul Koning <paulkoning at>
>>> ...
>> Ok. RSTS does indeed check for duplicate vectors. It also checks for devices interrupting at too high a priority.
>> It’s pretty neat code. Back in 1977 or so when that came out, it may have been one of the first autoconfig systems, at least in DEC. It could probe almost all devices supported by RSTS (and some not supported); the exceptions being card readers and the DT07 bus switch. But it would do hairy things like the KMC-11 and DMC-11, for example.
> Wait?  What was tricky about KMCs and DMCs?  They used the same algorithms, I had it down cold at the time.

For the KMC, you’d have to understand enough about that machine’s microcode to see how to make it request an interrupt.  For the DMC, in addition you have to find out how to get that device to execute a KMC instruction handed to it in a CSR — something that wasn’t all that obvious though it can be deduced from the manuals if you work at it.

> Speaking of which, I have one copy of the KMC-11A Programmer's Guide if anyone needs it or would like to scan it?

There are a couple on Bitsavers, but yours might be different from what is there.  Worth a look.


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