Shut down before power down?

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Douglas Crawford

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Sep 14, 2016, 1:29:31 PM9/14/16
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The pidp8 manual:

SYSTEM SHUTDOWN
Set the Sing_Inst and Start switches, then toggle Sing_Step to shut down the PiDP.
After 15 seconds, power can be cut off safely.
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Whats the risk? 
Can the emulated environment get corrupted by arbitrarily rebooting or cycling power on the Pi while pidp8 is running?
Also, mine does a linux shutdown with that procedure.  Intended functional change?
I did a lot of power downs and reboots before I read that.
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On Pi Zero with pidp8 installed over Jesse Raspian.

Oscar Vermeulen

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Sep 14, 2016, 1:35:31 PM9/14/16
to Douglas Crawford, PiDP-8
Doug,

The 15 sec wait before cutting power a is standard recommendation for the Raspberry Pi. Because it does not deal very well with protecting the file system and, judging from the SD card activity led, it only stops accessing the SD card after about 15 sec.

It is true - normally nothing bad happens. But on the other hand, I had to re-image a Raspberry Pi's SD card three times this year. Not because of ignoring the 15 second wait, to be fair. But because power got cut in the midst of a session or I was using a ho-hum power supply. SD card corruption is the Achilles heel of the Raspberry Pi...

Still, 15 seconds seems prudent as the activity led dies down after that.

Regards,

Oscar.
 

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Douglas Crawford

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Sep 14, 2016, 2:05:02 PM9/14/16
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Ah its a Pi thing.
Since the instructions were manipulating the SIMH/PiDP8 I thought we were protecting
the simulated environment.

Were there danger in powering down real PDP8s that required a shutdown procedure?

Douglas Crawford

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Sep 14, 2016, 3:05:52 PM9/14/16
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Now I understand my confusion.  I was thinking this had to do with just shutting down the emulation... no its about preparing to power off the  Pi.
Especially when you don't have a terminal attached to do that with Linux.
Which I assumed I'd always have, but if you are demoing a standalone PiDP8 then no you won't.
Very clever.
I didn't realize the Pi was that sensitive.  All these little embedded Linux things can be shut down at will... routers, etc.
So I didn't realize the danger.
I'll be much more careful now and always do a Linux shutdown prior to power off.




William Cattey

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Jul 28, 2017, 11:56:45 PM7/28/17
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My PiDP-8/i has a Pi-3, and I think waiting 15 seconds is actually too long.
The front panel lights go off almost immediately.
I count off 15 seconds, but after about 14 seconds, front panel lights start to light back up.

What gives?

Warren Young

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Jul 29, 2017, 12:42:12 AM7/29/17
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On Friday, July 28, 2017 at 9:56:45 PM UTC-6, William Cattey wrote:
My PiDP-8/i has a Pi-3, and I think waiting 15 seconds is actually too long.
The front panel lights go off almost immediately.

The lights go out when pidp8i-sim dies, not when the OS has finished shutting down.
 
I count off 15 seconds, but after about 14 seconds, front panel lights start to light back up.

That would be a reboot then, not a shutdown.

If you're doing this from the front panel with Sing_Step + Sing_Inst + Start and you're using my version of the software, that explains why you're getting a reboot instead of a shutdown. For mnemonic reasons, I changed that key combo, along with several others.

Bill Cattey

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Jul 29, 2017, 9:17:09 AM7/29/17
to Warren Young, PiDP-8
Yup.  That's it.  I've been using Oscar's instructions.  Somehow I missed the differing front panel commands.  Most likely I thought I read all the differences document, but never did.

I guess I've been lucky that I've not corrupted my SD card yet by doing the wrong thing.

-Bill
July 29, 2017 at 12:42 AM
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July 28, 2017 at 11:56 PM
My PiDP-8/i has a Pi-3, and I think waiting 15 seconds is actually too long.
The front panel lights go off almost immediately.
I count off 15 seconds, but after about 14 seconds, front panel lights start to light back up.

What gives?

On Wednesday, September 14, 2016 at 1:29:31 PM UTC-4, Douglas Crawford wrote:
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