Reset command crashes the system
Anthony A. Datri
convex!datri at uxc.cso.uiuc.edu
Tue Dec 11 10:43:22 AEST 1990
>(or OpenWindows), instead of using "reset", one should check out "kbd_mode
>-a" to clear up the console.
kbd_mode -a will put the console into a normal state -- sometimes after
the (mit at least) X server shuts down, the console is in a strange state
where every key seems to be interpretted as a return. I have xinit
aliased to
unset autologout; /usr/bin/X11/xinit >& /tmp/xinit.out ; kbd_mode -a
The redirect helps in debugging screwy .xinitrc files.
>The byte to be configured is location 0x1f:
> 00 - monochrome monitor
> 10 - ttya
> 11 - ttyb
> 12 - color monitor and 3/60 plug-in color frame buffer
> 20 - P4 Color frame buffer
Hmmmmm. I've run afoul of this before. When one purchased a color 3/60,
you got a cpu board without the bwtwo circuitry on it, but spare boards
all have the bwtwo. So, when you swap a color board with a spare, you end
up having two bwtwo's, and I've never quite figured out what effect that's
*supposed* to have. I have a couple machines like this that experience
strange behavior (up to and including spontaneous reboot) when reading
*certain* images.
This location is "documented" in /usr/include/mon/eeprom.h, where one can
find all *kinds* of interesting things. It says (4.1):
* 0x01f */ char eed_console; /* device to use for console */
#define EED_CONS_BW 0x00 /* use b&w monitor for console */
#define EED_CONS_TTYA 0x10 /* use tty A port for console */
#define EED_CONS_TTYB 0x11 /* use tty B port for console */
#define EED_CONS_COLOR 0x12 /* use color monitor for console */
#define EED_CONS_P4 0x20 /* use the P4 monitor for console */
Of course, it's not *really* clear from this file what "color" means. I
think that the repaired machines I mentioned above perhaps had this set to
0, and things worked okay as long as the on-board bwtwo didn't exist, but
when one started existing, all I got was blackness on the real console.
Poking around blind in an eeprom is great fun8^).
>Get to the PROM monitor (for example, "shutdown -hf now"). At the ">"
By the by, you can do this kind of stuff without shutting down -- just hit
L1-A, diddle away, and hit 'c' at the > prompt to continue. You'll want
to refresh your display, but it works fine. I once laboriously typed in a
custom logo this way, only to have the machine move to another desk a week
later.
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