Re: [TUHS] Fwd: Choice of Unix for 11/03 and 11/23+ Systems

[jnc@mercury.lcs.mit.edu (Noel Chiappa)]

    > It is definite, though, that Q22 memory won't work with an LSI-11/2
    > (M7270) ...  I'll try an LSI-11 (M7264) tomorrow, make sure it's the
    > same; it and the LSI-11/2 are similar enough that it should, but it'd be
    > good to confirm it.

Yes, it too won't work with Q22 memory (tried it, no go - ODT won't even start).


    > Then back to trying to work out why Mini-Unix is so fragile for me.

I tried some changes in the simulator set-up, to see if that would fix my
issue; no luck.

It's quite problematic: if I boot Mini-Unix on a clean copy of the RK pack, cd
to /usr/sys/dev, cp kl.c to nkl.c, and 'cc -c nlk.c', Mini-Unix reliably
restarts (trashing the disk in the process). (If I omit the 'cp', I can 'cc -c
kl.c' 3 times, and Mini-Unix restarts on the third.) Something's seriously
wrong.

I think before I try debugging it directly, I'll try one of the other
Mini-Unix repositories; the one I've been using (from Bob Eager's site) may
have some bit-rot.


    > From: Paul Riley <paul@rileyriot.com>

    > I'm checking with Peter Schranz about whether or not his RLV12/RL02
    > boards can run on the '03.

Dave Bridgham and I discussed whether the QSIC would work with an -11/03, and
that analysis should apply equally to the RLV12. Our conclusion was that it
should; here's our reasoning:

The device registers on the board should work fine on either Q18 or
Q22. That's because when going to the I/O page, the CPU asserts a special bus
line, BBS7 (that says 'this cycle is to the I/O page'). The device doesn't
look at the higher address lines when that's on, just BDAL00-12; so if the
LSI-11 is messing with some of BDAL181-21, it shouldn't matter.

For DMA cycles from the device to memory, since the CPU requires Q18 memory
to work, the device too should be able to read/write to Q18 memory. At least,
that's our theory.


I guess all this PDP-11 hardware detail isn't really on-topic for this list; I
should move it to Classic Computers, or something. Sorry all; it's
intermingled with early Unix stuff, and it was easier to keep it all in one
place.

	Noel