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

[Thomas Schmitt]

Hi,

> The current states of each of those drives seem to suggest that, with 
> those particular values, they would not be ideal for booting 
> purposes.

For me as half-educated user all three would look like
"normal" MS-DOS disks. So people buy pitfalls.

I cannot tell whether any of the FATs uses CHS. But the
weird H/C and S/H factors of 2 GB and 8 GB stick are
suspicious alone.
As said, their partition ends (LBA,C,H,S) have no integer
solution (X,Y) of the equation
  LBA = C * X * Y + H * X + (S - 1)


> If we take the ENDing CHS values as valid:
>  982 / 254 / 63 
> and we calculate the corresponding LBA:
>   ( ( 982 + 1 )
>  x ( 254 + 1 )
>  x ( 63 ) )
>  - 1
>    ___________
>    15'791'894 

Is this calculation generally valid ? It seems to assume that
the end is aligned to a full cylinder. (The start is not.)

It is clear that S/H must be 63 and H/C must be 255, because we
see the maximum possible values here. (H/C could be 256. But
that is outruled by Wikipedia about MBR.)

Nevertheless, this does not match the end LBA calculated
from start LBA and number of blocks.

Do i miss an essential point here ?


> If there is nothing to loose (some special feature in the USB drive, 
> data, etc.), probably it would be best to create a new partition 
> table, a new partition and then format them again.

Seems advisable, given the numerical madness.

This is were i see a gap in SYSLINUX wiki. The world could need
prescriptions for a non-weird partitioning and a LBA driven
filesystem.

While preparing an answer to Ronald, i re-read your mail of
17 Jan 2014 14:38:10 +0200, where you describe your test image.
One would need to derive hands-on instructions for MS-Windows
and Linux. (The latter might be in my reach, if i read enough
man pages.)


> @Thomas, If this email doesn't answer your questions, I hope at least 
> might be helpful anyway.

You were very helpful with this issue. Thanks a lot.
I was not even aware that there are CHS FAT and LBA FAT.

Can you sketch a prescription what a user should do to make
an USB stick best suitable for a SYSLINUX installation ?

Currently i am unsure what in your image is experimental and
what is recommendably traditional.
E.g. the disabled bootable/active flag seems to be non-standard
and we do not know for sure whether it is really needed for
Ronald's mainboard.

Biggest riddle for me, though, is how to achieve this with Linux
tools and MS-Windows tools. (I know /sbin/fdisk -lu. Everything
else i do by byte manipulations in images. Plumber style.)


Have a nice day :)

Thomas