18 Aug
2015
18 Aug
'15
8:29 p.m.
On Aug 18, 2015, at 2:00 PM, Johnny Billquist <bqt
at Update.UU.SE> wrote:
On 2015-08-18 19:05, Jon Elson wrote:
...
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.
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. 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.