On 2015-08-18 21:29, Paul Koning wrote:
On Aug 18, 2015, at 2:00 PM, Johnny Billquist <b...@update.uu.se> wrote:
On 2015-08-18 19:05, Jon Elson wrote:
...
Most likely, some board was added or removed from the system before you
got it, and it caused the vector to now be wrong.
The vector is usually not the first victim. The CSR address is, which cause all
access to the controller to fail. But the vector often also move, causing the
more obscure errors. However, most DEC OSes actually autodetected the vetor,
and did not care about the actual floating assignment rules for the vectors.
The thing is, all you need is to trigger an interrupt on the device, and then
notice at what vector it came in, and then you go with that. This only fails
when several devices happen to use the same vector.
Typically that would be detected as a configuration error — two devices whose
autodetected vector matches. One of the offending devices (the one seen later,
presumably) would end up disabled.
Ideally yes. However, at least RSX I think fails on that. As device
vectors are detected. they are installed. So the vector detection code
does not get called for the second device using the same vector, but
instead you get a spurious interrupt in the autoconfiguration.
But that is just some vague recollection, and I could be wrong. In
normal operations, RSX does not probe, but relies on what was discovered
during sysgen.
In some cases, you had to force a device to be at a non-standard
address, possibly because a 3rd party device could not be configured at
the address the DEC enumeration scheme wanted to put it at. This was
pretty easy to do in later VMS systems.
Very easy to do in RSX-11M-PLUS as well. A simple one line command, which can
be done on the running system.
And RSTS, starting with V5B.
Cool. I had no idea. Plain RSX-11M cannot. The CSR and vector is set at
sysgen, and you can (of course) patch the memory, but there is no
command to reconfigure the running system.
-11M-PLUS got all that as a part of the support for the 11/74, where you
were expected to be able to move devices around in the running system.
Hot-pluggable, in a way. And it also applies to CPUs, memory and
buses... It's a rather complex subsystem, but extremely nice.
Johnny
