On Sun, Feb 10, 2002 at 03:35:22AM -0500, Paul M Foster wrote:
> Okay all you geezers out there.... I've got a 486 that I've been using
> as a firewall. I'm trying to make it "headless", but when I remove the
> keyboard and try to boot, it won't get all the way through boot. It does
> the POST okay, and attempts to boot from the floppy, but won't finish
> booting. I've performed the test four times, twice with keyboard and
> twice without. Results are uniform.
>
> Now, it seems like I recall from a past life that old PCs used one of
> the keyboard lines to manage memory or somesuch. Seems like I remember
> something like an "A20" error or something like that.
>
> Anyone remember this, and am I on the right track?
>
> Paul
>
Okay, I had to search google for this.
Apparently, this problem indicates a problem with the 21st address line,
the A20 line. This line provides access to the high memory area, and is
normally controlled through the keyboard controller. The solution (as
someone mentioned) is apparently to disable the keyboard "halt on error"
setting in the BIOS. I didn't believe this would work, but next time I
put a monitor on the firewall, I'll check the BIOS and try it.
Of course, on the surface, this sounds like a really boneheaded move by
some desperate PC engineers. "Geez, how are we going to provide access
to the HMA; we don't have any lines left?" "Hey, let's use the keyboard
controller!" Argh.
Paul
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