[TUHS] Unix on an 11/23 (Was: Work I've done with a PDP-11 simulator)

[spedraja@gmail.com (SPC)]

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Great work, Noel. A lot of thanks (to you but for the rest of helpers too).

I'll keep a reference of this message and try it as soon as possible... the
disruptive fact (in terms of time) here is to put up-to-date both the
PDP-11/23-PLUS and RL02. Once I do that will embark on your hack.


Gracias | Regards - Saludos | Greetings | Freundliche Grüße | Salutations
​
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No crea todo lo que ve, ni crea que está viéndolo todo



2014-05-15 2:41 GMT+02:00 Noel Chiappa <jnc at mercury.lcs.mit.edu>:

>     >> I got one PDP-11/23-PLUS without any kind of disk (by now, I got one
>     >> RL12 board plus one RL02 drive pending of cleaning and
> arrangement)...
>     >> I guess if could be possible to run V6 in this machine. There's any
>     >> kind of adaptation of this Unix version (or whatever) to run under ?
>
>     > IIRC the README page for that set of disk images indicates that in
> fact
>     > they originally came off an 11/23, so they should run fine on yours.
>
> So I was idly looking through main.c for the Shoppa Unix (because it
> printed
> some unusual messages when it started, and I wanted to see that code), and
> I
> noticed it had some fancy code for dealing with the clock, and that
> tickled a
> very dim memory that LSI-11's had some unusual clock thing. So I decided I
> had better check up on that...
>
> I got out an LSI-11 manual, and it looked like the 23 should work, even for
> the 'vanilla' V6 from the Bell distro. But I decided I had better check it
> to
> be sure, so I fired up the simulator, mounted a Bell disk, set the cpu type
> to '23', and booted 'rkunix'. Which promptly halted!
>
> After a bit of digging, it turned out that the problem is that the 11/23
> doesn't have a switch register! It hit a kernel NXM trying to touch it -
> and then another trying to read it in the putchar() routine trying to do a
> panic(), at which point it died a horrible death.
>
> So I added a SR (you can create all sorts of bizarre hybrids like that with
> Ersatz-11, like 11/40's with 11/45 type floating point :-), and then it
> booted fine. The clock even worked!
>
>
> So you will have to use the Shoppa disk to boot (but see below), or we'll
> have to spin you a special vanilla V6 Unix that doesn't try to touch the
> SR -
> that shouldn't be much work, I only found two place in the code that touch
> it.
>
> I did try the Shoppa 'unix', and it booted fine on an 11/23.
>
> Two things to check for, though: first, your 11/23 _has_ to have the MMU
> chip
> (that's the large DIP package with one chip on it nearest the edge of the
> card), so if yours looks like this:
>
>   http://www.psych.usyd.edu.au/pdp-11/Images/23.jpeg
>
> you're OK. Without the MMU chip, most variants of Unix will not run on the
> 23
> (although there's something called MiniUnix, IIRC, which runs on an LSI-11,
> which would probably run on a /23 without an MMU).
>
>
> Here's the part that might be a problem: To run any of the Unixes on the
> Shoppa disk, you also have to have the FPP chip too (that's the second
> large
> DIP package with two chips on it - the image above does not include that
> chip, so if yours looks like that, you have a minor problem, and I will
> have
> to build you a Unix or something).
>
> All of the Unixes on the Shoppa disk have to have the FPP, except one - and
> that one wants an RX floppy as the root/swap device! The others will all
> crash (I tried one, to make sure) if you try and boot them on an 11/23
> without the FPP.
>
> I could try patching the binary on the one that doesn't expect to use the
> FPP
> to use the RL as the root, or either i) build you a vanilla V6 for a 23
> (above), or ii) figure out how to build systems on the Shoppa disk, and
> build
> you a Unix there which i) uses the RL as the root/swap, and ii) does not
> expect to have the FPP.
>
> But let's first find out exactly what you have...
>
>         Noel
>
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