[gPXE] GPXE floppy image dumps register.

[H. Peter Anvin]

On 01/07/2010 12:59 AM, Stefan Hajnoczi wrote:
> This happens when reading a track from the floppy fails.  The code is
> arch/i386/prefix/dskprefix.S:240.
> 
> The register state is that from int 13h ah=2, see
> http://en.wikipedia.org/wiki/INT_13#INT_13h_AH.3D02h:_Read_Sectors_From_Drive.
>  Here are the meanings of the registers:
> AL = Sectors to read count = 0x12 = 18
> CH = Track = 0x00 = 0
> CL = Sector = 0x01 = 1
> DH = Head = 0x00 = 0
> DL = Drive = 0x00 = 1st floppy disk ( "drive A:" )
> 
> It looks like it failed on the first read operation.  Does the floppy
> drive work?  Have you tried another floppy disk?
> 

It's quite common for floppy disks *especially*, and INT 13h in general,
to fail on the first read, due to BIOS timeouts set too low.  In
Syslinux I retry every read at least 6 times before giving up.

	-hpa