ISO: PDP-11/40 LTC and Stack Limit options

Noel Chiappa jnc at
Tue Nov 22 07:21:01 CST 2016

    > From: Josh Dersch

    > There appears to be no continuity between CA1/CB1 of slot 9 and CA1/CB1
    > of the SPC/MUD slots in the rest of the system.

Is that the only issue? If so, that should be 'not too hard' to track down.

It's possible that they didn't bother wiring NPG to that slot, but sent it
directly to the NPG pin on the 'UNIBUS out' connector; when the -11/40 was
done, there were no single-board DMA devices.

    > It's very puzzling.

BTDT! :-)

    > I have an RK11 and an RK05

Ah, you're good then - Unix V6 will run fine with a single RK. (Ah, memories:
my first experience as a sys-admin was on an 11/40 with a single RK...) The
standard V6 distro include systems that will run on an RK. (The V7 distro
does not, but it's possible to build RK-based systems. You'd need to bring it
up on an emulator to do so.)

    > (with the option of a 2nd RK05 if I ever get some mounting rails for
    > it.) I know the RK05s are tight storage-wise.

Well, you can't put all the source and documentation online with a single RK
(or even two), but that shouldn't be an issue. If you were actually trying to
do _real work_ on the system, a single RK might be something of a PITA.

    > I also have an RL02 but I need to repair an RL11 first.

Put that online, and you'll have plenty of room. Also, with two controllers,
you'll get higher performance (not that you care :-); you could put e.g.
swapping on the RK, and most files on the RL.

    > I should be able to wrangle bits onto media either using what I have,
    > or by using stuff at the LCM, but the VTServer option sounds nice too.

OK, I'll probably get back to work on it 'soon'.

    > The RL bootstrap and driver would be very useful to have, thanks!

They're available on my "Bringing up V6 Unix on the Ersatz-11 PDP-11
Emulator" page, here: 

That page (and it's partner, "Improving V6 Unix") probably contains some
other useful stuff, if you're serious about running V6.

One off the top of my head: the C on the 'vanilla' V6 distro is fairly
primitive. There are no longs or unsigneds, casts don't work, etc, etc. There
is a later version (which I think might be the so-called 'phototypsetter C'),
available from the 'Shoppa disks', you might want to get that.


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