On 2025-12-26 17:10, Anton Lavrentiev wrote:
> > So you just have to accept that your device sits somewhere, and as
> long as it isn't
> > colliding with anything existing on *your* system, you are fine.
>
> While it's technically correct for any particular system, my concern was
> that if a range
> was documented as already assigned, then it's better not to use it to
> avoid any potential
> conflict should the documented device be implemented in SimH (in the
> future). Because
> obviously, the addition of such a device would go "by the book" to use
> its reserved ranges.
> That would then save from unnecessary code (or configuration)
> modifications required for
> "custom" devices to move them out of the way.
Note that it's pretty hard to even find all addresses "reserved", as
most documents don't have complete lists, and even DEC reused some
addresses for multiple devices.
There are a "few" fixed, reserved addresses, but the majority of all
devices are expected to sit in the floating area, and that is probably
where you should place anything you create. The fixed addresses don't
make much sense to mess with.
But as you *really* need to have the address selection configurable
anyway, this really comes down to a choice for each user to pick
whatever address they fancy.
And when it comes to the floating address space, since you can't really
put a "rank" on your created device, it's just going to have to be just
be placed where nothing else sits.
If you want it to not mess with the autoconfiguration software that
might be run, you should really pick some high address in the floating
space, so that the scan stops before it even hits your device, since it
would just be confused and assume wrong if it even got there.
Johnny
> <mailto:
anton.la...@gmail.com
> <mailto:
anton.la...@gmail.com>>> wrote:
> >
> > > I didn't realize there was a convention, that makes life abit
> > easier :) I'll probably switch things over tofollow that.
> > Also, there's assignment for interrupt vectors (described in
> PDP11
> > handbooks). I'd suggest NOT to use any vectors what have an
> assignment.
> > These were specifically reserved for "users" (octal):
> > 170, 174, 270, 274
> > (vector 140 is reserved for AA11, a lightpen display)
> > Also, these seem to have been unassigned (from the "fixed"
> > assignment range):150, 154, 160, 164
> > Vectors above 300 (thru 777) are used for floating assignments.
> > UNIBUS address ranges have also been quite standardized, and
> again
> > 176400 (thru 176476) is assigned to AA11, so it is in
> conflict with
> > your device.
> > There are safer ranges, which have never beenassigned and
> are still
> > available.
> > E.g. see Appendix A in here:
> >
http://wwcm.synology.me/pdf/ <
http://wwcm.synology.me/pdf/>
> >
> EB-19402-20%20PDP11%20Processor%20Handbook%20PDP11-04-24-34A-44-70%20(1981).pdf <
http://wwcm.synology.me/pdf/EB-19402-20%20PDP11%20Processor%20Handbook%20PDP11-04-24-34A-44-70%20(1981).pdf <
http://wwcm.synology.me/pdf/EB-19402-20%20PDP11%20Processor%20Handbook%20PDP11-04-24-34A-44-70%20(1981).pdf>>
> > <mailto:
nicholas...@gmail.com
> <mailto:
nicholas...@gmail.com>>> wrote:
> >
> > Hi Anton,
> >
> > Thanks for the comments and suggestion about bit fields - I
> > didn't realize there was a convention, that makes life a bit
> > easier :) I'll probably switch things over to follow that.
> >
> > > The source code of what it'sbased on is rather off the
> > current open-simh repo;
> >
> > Ah, that makes sense! I startedwith code from https://
> >
github.com/obsolescence/pidp11 <
http://github.com/obsolescence/
> pidp11> <
https://github.com/obsolescence/ <
https://github.com/
> obsolescence/>
>
github.com/open-simh/simh> <
https://github.com/open- <https://
>
github.com/open->
> > simh/simh> I'll update my READMEs to note that.
> >
> > Cheers, -Nick
> >
> > On Wednesday, December 24, 2025at 9:38:03 PM UTC-8 Anton
> L. wrote:
> >
> > Interesting project! :-)
> > My comments:
> > 1. The source code of what it's based on is rather
> off the
> > current open-simhrepo;
> > 2. Most DEC devices follow a rather uniform
> convention for
> > bit assignments in CSRs:
> > <0> = GO
> > <6> = IE
> > <7> = RDY
> > <15> = ERR
> > I think it's bestto stick with these assignments for
> clarity.
> > Best,
> > Anton
> >
> > On Wed, Dec 24, 2025 at 11:53 PM Nick M
> > <
nicholas...@gmail.com
> <mailto:
nicholas...@gmail.com>> wrote:
> >
> > Hello!
> >
> > I've been enjoying playing with SimH and the
> PiDP-11 for
> > a little while now. I worked with the IMSAI 8080
> back in
> > theday, and before that pressed my nose against the
> > glass to look at the blinkenlights of a
> PDP-11/70, but
> > never had a chance to really dig into that machine,
> > until now :) I believe I will be building up a
> PiDP-11
> > front panel kit soon! but even just playing
> through the
> > SimH interface and Joerg Hoppe's simulated
> console has
> > been a blast! This group has been a great
> resource for
> > digging into the code, and a fun read for seeing what
> > others are working on.
> >
> > I got myself going on a pet project a few weeks back,
> > andwhile the original motivation sort of went
> away, the
> > project took on a life of its own. The basic idea
> is a
> > virtual device bus (named the PigBus) that
> connects to
> > theUNIBUS and allows the insertion of up to 255
> custom
> > devices. The main feature of this (vs. compiling
> custom
> > devices directly into SimH, akin to Oscar Vermeulen's
> > BMP180 device) is that once the PigBus is
> compiled into
> > SimH, new devices can be developed and connected
> to it /
> > without re-compiling SimH/. The system even
> allows hot-
> > swapping of devices on a running SimH system.
> >
> > This was my first time messing with SimH, so there's
> > surely a lot of things I did wrong (or perhaps not in
> > thebest possible way). Also, I don't claim that
> this is
> > particularly useful, or even necessarily interesting;
> > butI've had a lot of fun with it, it's been a good
> > excuse to learn a lot of new things (including more
> > about how SimH works), and so I thought I would share
> > it.The GitLab repository is
https://gitlab.com/
>
youtube.com/ <
https://youtube.com/>
> > playlist?list=PL2InzLo35oTeEa_T-
> > BDbRR4b5DVmKHSbX&si=7EsK9MB-UZ5cVwDk <https://
> >
youtube.com/playlist?list=PL2InzLo35oTeEa_T- <
http://youtube.com/
> playlist?list=PL2InzLo35oTeEa_T->
> > BDbRR4b5DVmKHSbX&si=7EsK9MB-UZ5cVwDk>
> >
> > Best wishes, -Nick
> >
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> --
> Johnny Billquist || "I'm on a bus
> || on a psychedelic trip
> email:
b...@softjar.se <mailto:
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> Reading murder books
> pdp is alive! || tryin' to stay hip" - B. Idol
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