> > I boot Linux via BIOS, then boot DOS via LINUX
> > when I boot linux again via LINLD, the "Uncompressing Linux ..."
> > takes a lot longer as compared to doing a LINLD from a DOS which
> > was booted by BIOS. I think this has something to do with
> > switching.... oh! I know .... machine_real_start() from linux turns
> > off the cache, so this could be the reason. Ok, so I'll check this
> > out by chaning CR0.
>
> It is utterly strange that you can boot DOS from Linux at all.
>
well, not really.
machine_real_start() from process.c switches into 16 bit mode. you can pass
arbitrary code to that function. this code has to:
reset some hardware ---
- reset 8259 interrupt controller, that is, IRQ mapping (IRQ0->INT8)
- reset 8253 timer to 18,2 ticks per second (I think)
and then:
- correctly initialize EBP, ESP to 0x7c0, SS to 0.
- also clear bits 16-31 of EAX, EBX ....
and as a last step:
- reset harddisk via int10
- read sector 0 to 0x7c0
- copy sector 0 to 0x600
- far jmp to 0:0x7c0
with this, I can boot DOS with EMM (goes into protected mode) or even
boot Windows2k-server. the latter only on my EPIA-ITX board, on another
board, it unfortunately crashes as soon as it goes into protected mode,
that is, the machine looks like its performing a cold-start (warm-start?).
seems like a double- or triple-fault. any idea on how this can be debugged?
thanks in advance,
herbert
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This archive was generated by hypermail 2b29 : Mon Mar 31 2003 - 22:00:22 EST