18 Aug
2015
18 Aug
'15
9:23 p.m.
Paul Koning <paulkoning at comcast.net> skrev: (18 augusti 2015 21:55:23 CEST)
Rsx do most, if not all of that in the sysgen autoconfig phase, but not during normal
boot.
At boot, device csr's are probed for simple read access. If nothing responds, the
device is put offline, but that's it. Detecting disk types is also a bit dynamic, but
with some restrictions.
Johnny
--
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On Aug 18, 2015, at 3:48 PM, Johnny Billquist
<bqt at update.uu.se>
wrote:
On 2015-08-18 21:29, Paul Koning wrote:
>
>> 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:
>> ...
>>> 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.
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.
Also, for disks it would discover all units and their types.
paul