[syslinux] USB boot problems on Gigabyte GA-M55Plus-S3G

[Pete Batard]

[disclaimer: I am the author of Rufus]

Hi,

On 2014.01.15 10:10, Thomas Schmitt wrote:
> As producer of MBRs i wonder where that LBA-flag is located.
> In bit 0 to bit 6 of byte 446 (where bit 7 means active/bootable) ?

I haven't looked at what GParted does, so I may be off mark, but I have 
a strong suspicion that this LBA "flag" is a fake flag that simply 
indicates if a FAT partition type was set as CHS (0x06, 0x0b for FAT16 
and FAT32 respectively [1]) or LBA (0x0e, 0x0c for FAT16 LBA and FAT32 
LBA respectively [1]).

Especially, I very much remember having to fix the partition types in 
Rufus after the Microsoft API went through the formatting, as I found 
that, even after you partitioned the drive and set LBA partition types 
for FAT, the formatting process would change the partition types to non 
LBA ([2] - also see the comment at line 822).

I seem to recall that, unless you did that, you would indeed run into 
trouble during boot.

Oh, since it might be useful for OP's testing, I should probably point 
out that Rufus can also be used to install a blank Syslinux v4 or v5 on 
an UFD (so you if you add something with a config file and some .c32, 
you should be able to test whether the Syslinux versions that are 
embedded in Rufus can boot). This is an advanced feature, so it is not 
available in default mode, but if you want to enable it, just click on 
the white arrow near "Format Options", so that you see the additional 
options panel. Once you do that, you should find that "Syslinux v4" and 
"Syslinux v5" are listed as extra options in the "Create a bootable 
disk" dropdown. Or you can see [3].

Regards,

/Pete

[1] http://en.wikipedia.org/wiki/Partition_type
[2] https://github.com/pbatard/rufus/blob/master/src/format.c#L838
[3] https://github.com/pbatard/rufus/wiki/FAQ#wiki-Advanced_Mode