Re: Booting linux using Novell NetWare Remote Program Loader

H. Peter Anvin
2001-09-13T10:14:33Z

Pavel Machek wrote:
> Hi!
>
>
>>>I found out I can boot it after little games with mars netware
>>>emulator. However I have problems booting anything else than
>>>freedos. Trying to boot zImage directly results in crc errors or in
>>>errors in compressed data. Too much failures and too repeatable
>>>(althrough ram seems flakey) for me to believe its hw.
>>>
>>I bet that's the same problem I had booting a zImage directly from an
>>El-Torito CD. The problem was the autoprobing for the floppy type
>>performed by the boot loader. It detected a 2.88 drive and issued
>>corresponding read requests (track x, 36 blocks; track x+1, 36 blocks;
>>...). The bios performs these request, but it emulates a 1.44 disk so
>>the last 18 blocks of track x are actually the blocks from track x+1.
>>In my case I did not even got a crc error but an immediate reboot.
>>
>>I removed the autoprobing from bootsect.S and fixed it to 1.44MB format
>>et voila, it worked perfectly.
>>
>
> Do you have patch to do that?
> Pavel

Sure... but he's hard-coding 1.44 MB format. This behaviour is also
quite common on for example USB drives; it is simply no longer correct
to expect the BIOS to reject invalid CHS geometries (if the underlying
drive is really an LBA drive most if not all BIOSes will simply apply
the conversion algorithm without limit checks.)

Can we please retire bootsect.S and get on with our lives? This thing
is becoming a millstone around our necks!

(For those that don't know, there is no way to determine the CHS
geometry of floppy media from the BIOS. The "get geometry" call on a
floppy drive returns what the drive is capable of, not what the current
medium is using. DOS and its relatives don't care, since a FAT
filesystem includes the CHS geometry in the superblock.)

-hpa