no, im not suggesting modify the console driver, im suggesting that as a 
last resort if you need to get into ddb and cant because the kernel
won't respond, drop to the console and fudge your way into ddb. if you make
a sufficiently correct stack frame for the entry, then it should be of 
some use to you. 
Isildur

On Mon, 19 Nov 2001, Bob Lantz wrote:

> Are you suggesting modifying the console driver??
> 
> Normally, I can enter DDB by hitting the "do" key - but in a crashed
> situation, this does nothing - machine dead, no panic, and no obvious way
> of determining *why* it is dead.
> 
> Is the "halt" button the button labeled with two slashes, next to the
> LED's, that doesn't appear to do anything when you press it?? Is there
> some way of activating it so that it will drop you into the debugger?
> 
> Or at least reset the system without power-cycling it? ;-/
> 
> Bob
> 
> On Tue, 20 Nov 2001, Lord Isildur wrote:
> 
> > well in a drastic situation you could (with the kernel's namelist) drop
> > to the console and twiddle the right bits to jump yourself into ddb :-)
> > it actually wouldnt be too hard. you might have to first look to see what
> > a normal entry to ddb would look like and fake that, build a stack frame
> > by hand and then set the pc, and then resume execution.
> > of course, one annoying thing about the later DECstations is that the halts
> > and so on are done in software that for some reason seems less robust as
> > each subsequent model came out, such that on the '240 and the '260 i have
> > encountered crashes in which the halt button did nothing.
> >
> > ymmv,
> > isildur
> >
> > On Sun, 18 Nov 2001, Bob Lantz wrote:
> >
> > > Arrgh. My DS5000/260 ran 1.4 flawlessly for nearly a year without
> > > rebooting. Since I upgraded (?) to 1.5.2, it has crashed four times -
> > > frozen completely. Each time, I can't enter DDB, so I have no idea:
> > > software crash? hardware failure? network problem? who knows?!!
> > >
> > > Does anyone have any suggestions of how to get information out of a
> > > machine that is just sitting frozen? Is there any way to get into
> > > DDB even if you're blocked in some normally non-interruptible state?
> > >
> > > I would just like to know what is going on...
> > >
> > >
> >
> 
>