G Finder and Crash recovery

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Neil Christie

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Jul 15, 1996, 3:00:00 AM7/15/96
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In article <4se5qc$2...@newsbf02.news.aol.com>, neil1...@aol.com
(Neil199999) wrote:

> Hi,
>
> While reading this newsgroup lat week, I read about typing the "apple" and
> power key and then typing "g finder" to recover from a crash. I had two
> crashes using Netscape and when I followed the above instruction, I
> recovered and was able to complete my tasks. So in short:
>
> What does g finder do and how come it isn't common knowledge.
>
> Neil

G is a resume command, I don't think it matters what you append to it.

Another good way to continue after crashes is to use the ExitToShell
command, here is an excerpt from Apple's Tech Info Library:

TOPIC ---------------------------------------------

What is the A ("ExitToShell") trap or address to call for
"Resume OS" from the ROM debugger on a Macintosh?

DISCUSSION ----------------------------------------

The most efficient way to call the "ExitToShell" trap with any
Macintosh with the ROM debugger is documented below. To use
this method, the interrupt switch must first be depressed to
generate the debugger window.

At the ">" ROM debugger prompt, type the following lines,
pressing Return after each:

SM 0 A9F4
G 0

In the first line, the "SM" stands for "Set Memory", the "0"
signifies memory location "0", and the "A9F4" is the trap
number for the "ExitToShell" trap. This line puts "A9F4" at
memory location "0". In the second line, the "G" stands for
"Go" and the "0" stands for memory location "0". This line
tells the computer to execute the instructions starting at
memory location "0". Since "A9F4" is at memory location "0",
the "ExitToShell" trap is executed.

Barring other memory corruption, your Macintosh should exit
back to the Finder. It is recommended that all other work in
progress be saved and that the machine be restarted to
completely clear and reset memory.

Neil.
--
Mac + Internet Guru looking for work in
Scotland, get in touch for more info.

Neil199999

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Jul 15, 1996, 3:00:00 AM7/15/96
to

Mike

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Jul 15, 1996, 3:00:00 AM7/15/96
to Neil199999


I don't know exactly what it does but I use it all the time with the Interupt Button. I
assume it is some Apple leftover DeBugger.

Mike

Mike

unread,
Jul 16, 1996, 3:00:00 AM7/16/96
to Jay Lee

The Interupt Button is one of the two buttons on the front of many, but not all Macs.
The other button is reset. I beleive they are there to help programmers, but they are
useful to an average user because sometimes, not all the time, they can get you back to
the Finder so you can save whatever you were working on before restarting. (I
wouldn't recommend continuing to work on the Mac without restarting as if notheing
happened after using the G Finder trick)

Mike

-->Note: I'm not sure if "Interupt Button" is the official name, but it sounds good ; -)

Jay Lee wrote:


>
> Mike <cha...@earthlink.net> wrote:
>
> >> I don't know exactly what it does but I use it all the time with the
> > Interupt Button. I assume it is some Apple leftover DeBugger.
>

> What the heck *is* the Interupt Button?
> The dialog box appears every now & then, and I don't know what caused it
> to appear.
>
> --
> Jay Lee (Capelle a/d IJssel, The Netherlands)
> jay...@sterbbs.nl
> j....@bk.tudelft.nl
> ## Windows95? Get the original:MacOS! ##

Aftab Khan

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Jul 17, 1996, 3:00:00 AM7/17/96
to

Mike wrote:
>
> The Interupt Button is one of the two buttons on the front of many, but not all Macs.
> The other button is reset. I beleive they are there to help programmers, but they are
> useful to an average user because sometimes, not all the time, they can get you back to
> the Finder so you can save whatever you were working on before restarting. (I
> wouldn't recommend continuing to work on the Mac without restarting as if notheing
> happened after using the G Finder trick)
>
> Mike
>
> -->Note: I'm not sure if "Interupt Button" is the official name, but it sounds good ; -)
>

Nah, its called the "Programmer's Key."

I can never get this to work. Normally I have MacsBug installed, and so
don't see the mini-debugger, but when I do "G FINDER" dosn't seem to
help me often.
You can also type
"SM 0 A9F4" [return]
"G 0" [return]
I have gotten this to work precisely once, and the Mac froze soon
afterwards anyway.
If you don't have a programmer's key, command-[power on] has the same
effect. If you're serious about all this, install MacsBug (bearing in
mind it hogs ~500K of RAM).

Regards,
Michael Hudson

Please don't email this address - it's not mine.

Kevin McMurtrie

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Jul 17, 1996, 3:00:00 AM7/17/96
to
(Neil199999) wrote:

>Hi,
>
>While reading this newsgroup lat week, I read about typing the "apple" and
>power key and then typing "g finder" to recover from a crash. I had two
>crashes using Netscape and when I followed the above instruction, I
>recovered and was able to complete my tasks. So in short:
>
>What does g finder do and how come it isn't common knowledge.
>
>Neil

The interrupt brings up the ROM debugger. When you type "G FINDER" you
are entering an invalid command that, by luck, usually crashes you out of
the current program.

The "G" command causes CPU execution to begin at the given hexdec address.

The more reliable method is:


SM 0 A9F4
G 0

This sets the ExitToShell trap code at location zero and then executes it.

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