Syslinux - Nov 2013 - Sysinux 6 will not boot ISOs on BIOS (i.e. pre-UEFI) systems

Hi,

hpa wrote:
> -               mov dx,cx
> +               movzx edx,cx
Gerardo Exequiel Pozzi:
> Yes! Fixed :)
> (maybe garbage in high word of "edx"?)
I am now pondering too, why my machine booted from high LBAs.

I understand that the new code zeros the upper 16 bit of EDX.
Was there remaining garbage from early BIOS activity before
isolinux.bin got started ?
Does my BIOS perhaps clean registers before handing over
control ?


Have a nice day :)

Thomas

On 11/26/2013 08:14 AM, Thomas Schmitt wrote:
> Hi,
> 
> hpa wrote:
>> -               mov dx,cx
>> +               movzx edx,cx
> Gerardo Exequiel Pozzi:
>> Yes! Fixed :)
>> (maybe garbage in high word of "edx"?)
> 
> I am now pondering too, why my machine booted from high LBAs.
> 
> I understand that the new code zeros the upper 16 bit of EDX.
> Was there remaining garbage from early BIOS activity before
> isolinux.bin got started ?
> Does my BIOS perhaps clean registers before handing over
> control ?
> 
Yes, that is the most likely explanation.

I think the high half of EDX might be unused up to this point, so if
there is garbage in it, this is where it would fail.

	-hpa

On 26.11.2013 17:14, Thomas Schmitt wrote:
> Does my BIOS perhaps clean registers before handing over
> control ?
Hardly anyone reads manuals these days.
LoL!
Bee awesome.:!


poma

Hi,

poma wrote:
> Hardly anyone reads manuals these days.
There are manuals ?

El Torito just specifies how to direct the BIOS to the
boot image, and what the boot image can learn from the
BIOS about its origin.
Possibly this silently builds on MBR specs. But about
those i can only find wikipedia rumors:
"the CPU is in real mode and the general-purpose and
 segment registers are undefined"

Last time i did machine code was with the 6502 of my
VIC-20, because Microsoft BASIC was so darn slow.


Have a nice day :)

Thomas