Re: [OpenBIOS] Why protected mode?

[AndreasHofer]

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>

On Thu, 8 Jul 1999, Brian Hurt wrote:
> Unless I'm missing something, the linux boot sequence uses IBM-PC BIOS
> functions.  I found a number of int 0x13 (diskette services) and int 0x10
> (video services) calls in arch/i386/boot/setup.S.  Even Grub makes heavy
> use of BIOS services- a quick grep revealed 23 different BIOS calls,

using
> services 0x13 (disk), 0x10 (video), 0x1a (RTC), and 0x16 (keyboard).

That's not a problem -- these are not mandatory and even now there are
some people that run Linux on ia32-based embedded systems.  They have no
BIOS and the kernel is started from flash memory.

Hi, Brian,

that is exactly what I was looking for all the time --- just booting Linux
on a bare machine whithout any BIOS. Could you give me some pointers on
that?

Andreas
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Why protected mode?

[Kevin Lawton]

AndreasHofer wrote:
> Hi, Brian,
>
> that is exactly what I was looking for all the time --- just booting Linux
> on a bare machine whithout any BIOS. Could you give me some pointers on
> that?

One of the guys from FreeMWare compiled a trim Linux which
could be loaded straight into the memory of bochs and
soon in FreeMWare without needing the BIOS.  We used
some hacks in bochs to set up the CPU registers in
protected mode etc.  It works.

Essentially, we didn't want to implement the 16bit stuff
for now, and wanted to boot straight into 32bit protected mode.

Seems like you could do the same thing, putting the Linux
image in a ROM rather than read it from a file etc, and
ROM'ing just a little startup code too.

-Kevin
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