[coreboot] APM and VESA

Marc Jones marcj303 at gmail.com
Tue May 31 18:50:15 CEST 2011

On Sun, May 29, 2011 at 1:55 PM,  <cinap_lenrek at gmx.de> wrote:
> Hi,
> working on a bootloader, we added apm initialization code to the bootloader
> so the kernel doesnt have to switch to realmode and can just do 32 protected
> mode calls.
> the bootloader does the following things in realmode before starting the kernel:
> 1) do apm installation check (INT 0x15, AX=0x5300)
> 2) do apm disconnect (INT 0x15, AX=0x5304)
> 3) do apm connect to 32bit protected mode interface (INT 0x15, AX=0x5303, BX=0)
> 4) save and pass the register contents after the connect call in some form to the kernel
> but doing this seems to disable VESA bios functionality on some machines (via epia
> and p3-sbc) (INT 0x10, AX=0x4F00 doesnt return any modes)
> i dont have the machines where this happens and i dont know the exact return
> conditions of the vbe calls yet, but i plan to debug this using our realmode emulator
> but it might take us some time...
> my question is are we on the right track? is it possible that doing these APM
> calls disables VBE?
> --
> cinap

Hi cinap,

It sounds like you may have an interrupt vector chaining problem or
register corruption problem in you interrupt installation.



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