Supermicro MBD-A1SAi-2550F

karu.pruun karu.pruun at
Tue Jun 24 06:47:45 PDT 2014

On Tue, Jun 24, 2014 at 12:35 AM, Roman Neuhauser <neuhauser at> wrote:
> now, before i get to boot-debugging-related questions...

I did some debugging and made some progress but no solution yet. I
compared the sys/boot/pc32/boot1.S of DFly and FBSD and found that
DFly got stuck in the subroutine seta20 that enables the A20 gate. (I
put some putstr-s around the loop; unfortunately no gdb in this
situation.) FBSD code has a timecount which exits the loop without
enabling it if enough time has passed, so it gets through the loop.
The reason DFly got stuck was that apparently apple has discarded
legacy hardware A20 and DFly was spinning forever in that loop trying
to set the gate. Interestingly, DFly's cdboot has that timecount,
otherwise it would not boot on a macbook either. So I got boot1.S to
print a char just before jumping to boot2 at line 265. However, it did
not get to boot2. I have no idea why.

Any ideas how to debug or where to look further?



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