Subject: Re: Retro computing to an extreme?

From: [email-masked] (Don Stokes)
Date: 21 Dec 93 08:10:00 GMT

[email-masked] (Charles Lasner) writes:
> I also heard the tale of the emulated faster -8 on the WCS 11/60.  And that it
> could run anything that an -8/e (with the same peripherals) could.  But not
> that it was ever used for anything beyond a hack in-house demo.  You can't
> build WPS from the sources, unless you have an additional more powerful disk
> device on the machine.  But since there aren't any other truly compatible
> peripherals between 11/60 and Omnibus, and the WPS developers weren't
> particularly inclined to move all the files on many RX01/02's (assuming the
> 11/60 had an emulated pdp-8 disk on it and someone had managed to somehow
> get a bootable OS/8 system to the emulated disk, etc.), any form of
> "development" on the 11/60 seems pretty unlikely.

I believe the 11/60 story, simply because having your binary able to run
on the same machine as your cross-development tools and source code would
be worth the tweaks required to get it to map onto the 11/60 and (I
believe) RSTS/E.  RSTS/E is useful for this sort of thing because of its
support for multiple run time systems; you'd just tell the standard monitors
to go play in the traffic while you run your own that could cope with the
PDP-8 emulating microcode.

Sure, the inner core stuff would have to be tested on a real live PDP-8,
and the final testing would likewise have to be done there, but you can
get a heck of a lot more done if you pile all your developers onto a
reasonable sized timesharing system with one copy of the source code,
cross-development tools and a binary environment to test the higher level
stuff.

--
Don Stokes, Network Manager, Victoria University of Wellington, New Zealand.
[email-masked](home) [email-masked](work) +64 4 495-5052 Fax+64 4 471-5386

---

From: [email-masked] (Charles Lasner)
Date: 21 Dec 1993 18:05:41 GMT

>cross-development tools and a binary environment to test the higher level

Your belief doesn't match the situation.  After loading the WCS, the
machine is no longer an -11, and doesn't even run RT-11, much less RSTS. 
Assuming a composite was developed, what's the overhead in allowing some
-11 cycles and some -8 cycles?  The whole point of the hack was to run a
faster -8, not a slower one.

In any case, RSTS never offered PDP-8 programmers any useful development
tools.  The sources of WPS are written in PAL8, and are assembled using
batch files meaningful only to OS/8.  Further, these batch files demand
that a reasonably large disk device house all of the relevant source files
at once.  The only way all of this can be met is if:

1)	The emulated PDP-8 already has an emulated disk since no physical
disk larger than an RX02 can be moved between an actual -8 and an 11/60. 
The WCS hack predates the RL01.  All of the other peripherals that
dismount aren't media-compatible between systems.  The media of choice of
WPS developers was RK8E, which can't be read on an -11.

2)	All of the files would have to be tediously moved across from an
-8 on RX01/02 and then reconstructed on the mythical disk on the
simulator.  There are quite a few files, and it's not likely any developer
would do it; more time is lost in the translation than is saved by the
speed-up.  Unless a machine was definitely available to leave sources
around on (frowned upon by management!) the developer can't work unless
that particular machine is available (definitely frowned on by
management!).  The alternative of carrying around one RK8E pack
(confirmed to be just about the capacity needed to develop the whole
system) looks a whole lot brighter; it was the method of choice of all
other PDP-8 system developers at the time, etc.

3)	WPS sources maintained on OS/8 produce a binary that writes itself
out on the RX01/02, which is then stand-alone booted for test.  The
program is I/O bound and wastes the speed-up hardware.  Even so, the whole
thing assembles on a real PDP-8/e in about 10 minutes, assuming you want
to assemble it all every time.  How much time is saved if a loaded machine
that emulates a PDP-8 2-3 times as fast when it's not doing anything else
is being used for multiple users?  The typical PDP-8/e system in-house at
that time had its own line-printer, possibly shared by an adjacent similar
system.  TECO was the editor of choice, and is freely available on OS/8.
 
There were many such machines available then; most also had fast RF08 head
per track disks on them.  Some also had special peripherals on them for a
specific project.  (I got bumped a few times from these systems because
the developer of the special-purpose project needed that particular
machine, etc. I would just move to another machine, since (at night
anyway) there were always more systems available, etc.) There were few
11/60's where the -8 hack exists.  Why would someone used to carrying
around a listing and an RK pack seeking an available system want to carry
around a double-box of RX01 media and wait for it to get loaded/unloaded? 

The way I heard it was that the hack was definitely done, but only for
curiosity value.  If you know the development history of the source files
of WPS, it just doesn't make sense that it was used for that purpose. And
WPS isn't that big a project anyway! Moreover, throughout all of the OS/8
stuff I "inherited" over the years, there has never been a mention of a
mythical device for an emulator. (There have been some arcane projects
vaguely in the same category, but each has a specific unrelated purpose,
etc.) (Of course this doesn't prove that there wasn't an emulated RF08!)

Unless the complete environment of the PDP-8 is emulated, people just
aren't interested in it.  RSTS never even came close.  Even PAL10 and a
PDP-10-based emulator (forget the name!) didn't cut it.  Most stuff
cross-developed was brought back to the hardware;once OS/8 became viable,
cross-development virtually ceased.  This is why PAL10 isn't language
compatible with PAL8 on too many key points.  Even though relatively minor
to implement, no one bothered to keep them in sync on features, etc.

Remember the timing: this is pre-DECmate WPS!

cjl