[TUHS] LSX issues and musing

Gavin Tersteeg gctersteeg at gmail.com
Tue Jul 12 07:37:32 AEST 2022

A lot of it was me just learning how V6 works in general. Getting V6 to
boot on a simulated 11/23 was pretty easy (I had some issues getting it to
compile at first, but it worked after I got that sorted out). Adding the
RL02 and RX02 drivers was a tiny bit more difficult. I would say that the
most difficult part was writing a RX02 boot program, trying to fit that
into 512 bytes with interleave code took a few days.

You were right about the source of the issue. I incorrectly assumed that
the EIS flag was only set in header.lsx.s, but it is also set in param.h.
The default param.h has the EIS symbol define commented out, while
header.lsx.s has it uncommented. By uncommenting the define in param.h and
recompiling decfd.c, it allows the kernel to be successfully linked. The
current kernel that builds is too big to be used with a 16K kernel size,
but I think I just need to recompile everything with the new param.h, and
maybe adjust a few other parameters.

I will look into getting an EIS chip. I'm probably going to move up to the
20K kernel size regardless, as I need the extra memory for changes that I
want to make to the kernel. I am betting that the "0: Missing temp file"
thing is due to some sort of file I/O issue, so I'll read into the compiler
source to see what is generating it.

On Mon, Jul 11, 2022 at 4:24 PM Noel Chiappa <jnc at mercury.lcs.mit.edu>

>     > From: Gavin Tersteeg
>     > I spent a lot of time getting UNIX V6 working on my PDP-11/23 system.
>     > It took a lot of tinkering with the kernel and drivers to make it
> work
>     > in the way I wanted to
> You must have made a lot of changes for it to take "a lot of tinkering".
> Bringing V6 up on the /23 has been done several times, and when I did
> it, it only took about 2 dozen lines of code in about 2 files. What all
> did you wind up changing?
>     > From my research, it seems like there were two different UNIX
> variants
>     > that could run on a system like this. These variants were LSX and
>     > MINI-UNIX. MINI-UNIX seems to require a decent mass-storage device
> like
>     > a RK05 and some porting to work on an 11/03, while LSX is designed to
>     > work on exactly the hardware specs that I have on hand.
> Bringing up MINI-UNIX on the /03 has been done at least twice; once
> historically (now lost, AFAIK), and again recently:
>     http://ana-3.lcs.mit.edu/~jnc/tech/unix/Mini/Mini.html
> I'm not sure what you're basing the "MINI-UNIX seems to require a decent
> mass-storage device like a RK05" on - it should run as well on whatever
> you're running LSX on as LSX does.
> I haven't run LSX myself, but from what I've seen, the only significant
> difference between the two is that LSX will run with less main memory than
> MINI-UNIX (which really kind of needs 56KB; LSX you can probably get away
> with 40KB).That was a significant issue when the LSI-11 was originally
> released, but these days one has to really work to have a QBUS PDP-11 with
> less than 56KB.
>     > my EIS-less 11/03
> EIS chips can be found on eBait for not much money (I just bought a couple
> myself), and it's worth investing in one, so on can dispense with the
> emulator, which takes real memory for which a better use can be found.
>     > The first issue is that the C compiler will randomly spit out a "0:
>     > Missing temp file" when attempting to compile something. This is
>     > annoying, but circumventable by just running the same command over
> and
>     > over until it works.
> Schaeffer's Law (from Larry Niven): anything you don't understand
> might be dangerous. I'd track down why this is happening.
>         Noel
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