[Simh] SimH - PDP8 non existent io devices

[Warren Young]

On Sat, Dec 15, 2018 at 12:21 PM Harold Bell <hhbell370 at att.net> wrote:

> I am mucking around with focal69


Which version? There are two major versions, the paper tape version and the
OS/8 version. I assume there are more versions floating around beyond those
two.

Can you point us to the source of the media images you're using? If it's
the paper tape version, please also point us at the instructions you're
using for loading it.

You may be interested in the PiDP-8/I software distribution:

    https://tangentsoft.com/pidp8i/

It is known to run on many more types of system than just the Raspberry Pi
with the PiDP-8/I board attached:

    https://tangentsoft.com/pidp8i/wiki?name=OS+Compatibility

In fact, the upcoming version has a mode to drop the PiDP-8/I specific
extensions to the simulator entirely, allowing it to run faster. We're
hoping to get that out before Christmas. Yes, Christmas *this year*. :)

If you don't want to use our entire software distribution, we also have
pre-built OS/8 RK05 media that you can use with your existing copy of
SIMH's PDP-8 simulator:

    https://tangentsoft.com/pidp8i/#os8

This media includes U/W FOCAL V4E, a significantly more powerful
implementation of the language than DEC's original offering. We've got a
lot of documentation on this in the project repository, much of it either
unique to our project or hand-converted and cleaned up by us, then stored
in our repository in web-accessible formats. The cleaned up documents come
from OCR'd PDFs you can find elsewhere, but the OCR job on some of them is
terrible, making them difficult to search.

Start with our U/W FOCAL Manual Supplement and then branch out from there:

    https://tangentsoft.com/pidp8i/doc/trunk/doc/uwfocal-manual-supp.md

If you really want DEC FOCAL 69 for some reason, we also offer that by
configuration when building the PiDP-8/I software distribution from source:

    https://tangentsoft.com/pidp8i/doc/trunk/README.md#enable-os8

You can have it installed alongside U/W FOCAL or instead of it. Keep in
mind that an RK05 disk pack is only 2.5 MB, and OS/8 divides it into two
logical devices due to the way it addresses the sectors, so you have to be
careful how much software you load onto the system half of your OS/8 RK05
boot media.

when it initailizes it seems to refer to non existent io device numbers


The PDP-8 architecture refers to devices by number in IOT instructions
which set aside 6 of their 12 bits for the device number. If you aren't
using a pre-configured simulator, such as our PiDP-8/I software
distribution, you have to configure SIMH to have the needed devices. The
PDP-8 supplement to the SIMH manual tells you what devices are currently
available in SIMH, and the main SIMH manual tells you how to enable them in
the simulator:

    https://tangentsoft.com/pidp8i/uv/doc/simh/main.pdf
    https://tangentsoft.com/pidp8i/uv/doc/simh/pdp8.pdf

Those are PDFs converted from the Word DOC files shipped by the SIMH v4
project on GitHub. They were updated less than a week ago, so if there's
any discrepancy in the docs vs the simulator you're running, it's that your
simulator is too old to have all of the features described. :)

Because there are only 64 unique device code in the PDP-8 architecture, and
the PDP-8 was one of the most popular computers of all time, some of them
got reused. This is most common in the case of "replacement" devices: the
TD8E DECtape transport controller effectively replaced the earlier TC08 on
PDP-8/e computers, so it reused its predecessor's device code, 77. You
therefore have to be careful to supply not only *a* device 77 in your SIMH
configuration, but also the *right* device 77.

PDP-8 software is often hard-coded to assume one particular device, since
there isn't enough core memory space to have fallback implementations for
every possible device. Sometimes you have software like OS/8 which lets you
re-build it with a different set of devices, but the basic point is the
same: at any one time, OS/8 supports only one device 77 type. You have to
rebuild the OS to get it to use a different type.


> I can't find any google references to.


You can search the bitsavers document collection on archive.org. Beyond
that, adding "pdp-8" to your search often helps.
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