freedos-user  

Re: [Freedos-user] Error loading OS: FAT32-LBA problem or something else?

Eric Auer
Sun, 25 Oct 2009 11:33:43 -0700

Hi!

> After "installing" FreeDOS on a FAT-32 partition, I attempted to boot
> it in a couple of ways, each of which resulted in the message:
> 
> Error loading OS

Maybe your FAT partition is not marked active or you did not SYS it?

> mbrfix (an open source program for NT/XP/etc.) reported cylinders
> 19457, tracks 25, cyl 64; first partition 38279 Mb type 7 (NTFS),
> second 894 Mb type 12 (FAT32-LBA).

Sounds okay...

> sys C:
> 
> which reported sectors/trk: 63, heads: 255 hidden: 78397200 FAT
> starts at 4AC3F10 + 26 (78397200 + 38) Boot sector load seg ... 60h

The hidden means that the partition starts after 78397200
sectors (of 512 bytes each) of something else. A better
name would probably be partition offset but the field in
the data structure apparently is even older than the idea
of having multiple partitions, so originally it was used
to reserve hidden space before the start of a FAT disk...

SYS may have accidentally made a CHS boot sector while you
needed LBA. You could try using another / newer version of
our SYS. Other people on this list will probably suggest
some :-). In Linux, you can also use sys-freedos-linux, in
particular the "sys-freedos.pl" perl script. You need to
install nasm first to run this :-). The script basically
calls NASM to compile a DOS boot sector and then updates
some values in the boot sector to match your partition.

Make sure that you run it only on a FAT partition, not
on other partitions and not on whole disks!

> Does anyone have insight into this?  Is it the 1024 cylinder problem?

Only if SYS happened to select a CHS boot sector for you.
You need a LBA boot sector here...

> it.  (Is Perl installed with FreeDOS?

Yes but the script is for Linux ;-)

> Or would I use Cygwin Perl under XP?

There are other tools for XP I guess...

Eric

PS: Please mail me off-list if you need help for using sys-freedos.pl



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