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* [TUHS] CSR in V6
@ 2022-02-27  0:29 Will Senn
  0 siblings, 0 replies; 2+ messages in thread
From: Will Senn @ 2022-02-27  0:29 UTC (permalink / raw)
  To: TUHS main list

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I noticed in v6 source that putch in prf.c - the system kernel printf's 
character routine, only prints to the console if the Console Switch 
Register is non-zero.

My question is  - how did y'all run things - with CSR zero and no kernel 
messages (seems dangerous to me, being naive and all) or with CSR 
non-zero and kernel messages.

On my FreeBSD instance, I value the messages that show up on console as 
they've alerted me to big problems in the past, but on my Mac, not as 
much (sure you can run Console and see them, but they aren't immediate).

Oh, BTW, I know I've seen this noted elsewhere, but I can't remember 
where. Dennis's v6 doesn't have the Western Electric message:

    mem = 435
    RESTRICTED RIGHTS

    Use, duplication or disclosure is subject to
    restrictions stated in Contract with Western
    Electric Company, Inc.

It was a bit of a head scratcher as I was trying to read from the Dennis 
version of the distro on my mac while running Wellsch's tape on simh. I 
spent quite a while spinning my wheels looking for "Western" in the 
files to no avail. I thought something was screwy with the files or my mac.

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^ permalink raw reply	[flat|nested] 2+ messages in thread
* Re: [TUHS] CSR in V6
@ 2022-02-27  7:38 Noel Chiappa
  0 siblings, 0 replies; 2+ messages in thread
From: Noel Chiappa @ 2022-02-27  7:38 UTC (permalink / raw)
  To: tuhs; +Cc: jnc

    > From: Will Senn

    > My question is - how did y'all run things - with CSR zero and no kernel
    > messages ... or with CSR non-zero and kernel messages.

On the -11/45 V6+ at MIT, we didn't have a printing terminal on the console,
just a VT52. We had a tool at MIT called 'dmesg':

  http://ana-3.lcs.mit.edu/~jnc/tech/unix/man8/dmesg.8

which made up for that a bit.

We normally ran with the CSR set to 173030 - the 'boot in single-user'
setting. That's because at one point the machine was in the 9th floor machine
room, but the console VT52 was on the 5th floor (where our offices were - the
famous print of the GE-645 Multics was on the hallway wall outside mine :-),
and I'd added a 'reboot()' system call (nothing fancy, it just jumped to the
bootstrap ROM), so we could reboot the machine without going up in the
elevator (not if it had crashed, of course). Later on, after we'd done with
kernel hacking (adding a network interface, and IP), and the machine stayed up
for long periods, we moved the console up next to the machine (since if it
crashed, you had to use the front panel to restart it, so you had to be up
there anyway); we stayed with the default CSR setting, though. (If it panic'd,
you could see the reason why when you went to reboot it.)

    > Oh, BTW, I know I've seen this noted elsewhere, but I can't remember
    > where.

Maybe at:

  https://gunkies.org/wiki/UNIX_Sixth_Edition#Distros

which discusses it?

	Noel

^ permalink raw reply	[flat|nested] 2+ messages in thread

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