Making a boot disk without Sys.com 
Author Message
 Making a boot disk without Sys.com

OK....i have the system files on a disk but its not bootable how do i make
the disk bootable using debug? :)


Sat, 13 Oct 2001 03:00:00 GMT  
 Making a boot disk without Sys.com

Quote:
>how do i make
>the disk bootable using debug?

You'd need to write a boot sector that's smart enough to bootstrap the OS.

Why not just use SYS?

 Tony



Sat, 13 Oct 2001 03:00:00 GMT  
 Making a boot disk without Sys.com
because cih trashes peoples pc's and with out going into it they need a way
to make a boot disk ...in a o/s that doesnt care about what ver of dos is
currently running...most ms dos stuff says wrong ver if the file isnt the
same ver ...so i want to make a boot disk with debug

Quote:
> >how do i make
> >the disk bootable using debug?

> You'd need to write a boot sector that's smart enough to bootstrap the OS.

> Why not just use SYS?

>  Tony



Sat, 13 Oct 2001 03:00:00 GMT  
 Making a boot disk without Sys.com

Quote:
> because cih trashes peoples pc's and with out going into it they need a way
> to make a boot disk ...in a o/s that doesnt care about what ver of dos is
> currently running...most ms dos stuff says wrong ver if the file isnt the
> same ver ...so i want to make a boot disk with debug

Have you considered that boot disks are specific to OS's? For example, SYS
installs 2 files (generally io.sys + msdos.sys) that between them boot up
the computer and define much of dos (eg: the ability to run a program).
Command.com called the command interpreter as this is it's function - it is
primarily a user interface.  There is no such thing as a magical 'generic'
boot disk.  That said, it would be be possible to make a replacement for
io.sys + msdos.sys that would be compatible with all msdos versions, but
you'd need to know quite a lot about the specifics of the various versions
of dos.  Probably the simplest way to achieve the same effect would be to
store the {binary images of the io's and msdos's for all the versions of
dos you wanted to work with} on a floppy disk, and have a small assmbler
program in the boot sector to load the appropriate one into memory.

- Benjamin.



Sun, 14 Oct 2001 03:00:00 GMT  
 Making a boot disk without Sys.com
if i had io.sys and msdos.sys and command.com from win 95 and the boot
sector needed for those specific files that is a boot disk so i placed the
boot sector info in a data segment and i write it "witha program " to the
blank boot sector on a disk.... :)

Quote:
> > because cih trashes peoples pc's and with out going into it they need a
way
> > to make a boot disk ...in a o/s that doesnt care about what ver of dos
is
> > currently running...most ms dos stuff says wrong ver if the file isnt
the
> > same ver ...so i want to make a boot disk with debug

> Have you considered that boot disks are specific to OS's? For example, SYS
> installs 2 files (generally io.sys + msdos.sys) that between them boot up
> the computer and define much of dos (eg: the ability to run a program).
> Command.com called the command interpreter as this is it's function - it
is
> primarily a user interface.  There is no such thing as a magical 'generic'
> boot disk.  That said, it would be be possible to make a replacement for
> io.sys + msdos.sys that would be compatible with all msdos versions, but
> you'd need to know quite a lot about the specifics of the various versions
> of dos.  Probably the simplest way to achieve the same effect would be to
> store the {binary images of the io's and msdos's for all the versions of
> dos you wanted to work with} on a floppy disk, and have a small assmbler
> program in the boot sector to load the appropriate one into memory.

> - Benjamin.



Sun, 14 Oct 2001 03:00:00 GMT  
 Making a boot disk without Sys.com

Quote:

> if i had io.sys and msdos.sys and command.com from win 95 and the boot
> sector needed for those specific files that is a boot disk so i placed the
> boot sector info in a data segment and i write it "witha program " to the
> blank boot sector on a disk.... :)

  In addition to writing the boot code to the boot sector of the floppy,
and copying those files to the floppy, SYS.COM also makes sure that the
location of the files on floppy is consistent with the only partial
understanding of FAT12 present in the DOS boot code (is this still true
in Win95? I'm not sure).  A boot sector with full understanding of a
FAT12 FAT and root directory is easy to write, but last time I looked,
MS hadn't.

  So where were you planning to get the boot code from?  I can think
of several possibilities, but I lost track of who originally asked
what in this thread.

  My PARTCOPY program (PCOPY??.ZIP on my web page) may be the easiest
way to copy the boot code to a floppy.  It may also be the easiest way
to copy boot code from a floppy or a partition on a hard drive.
Use with care.  It is easier than debug or coding int13h calls, but
don't let that give you a false sense that it is safer.

  DOS used the same boot code on a FAT12 floppy as it used on a FAT16
hard disk partition.  I think Win95 does too, but don't trust me.  If
you have a bootable FAT16 hard disk partition, partcopy can read the
boot code from it.
--
http://www.erols.com/johnfine/
http://www.geocities.com/SiliconValley/Peaks/8600/



Sun, 14 Oct 2001 03:00:00 GMT  
 Making a boot disk without Sys.com
i used sys.com to do a floppy then used debug to copy the boot sector from
the disk then i wrote teh asm file and put the copied sector in teh data
segment and then the compiled exe file and ran it and also put the system
files on the disk and it worked.......:)


Quote:

> > if i had io.sys and msdos.sys and command.com from win 95 and the boot
> > sector needed for those specific files that is a boot disk so i placed
the
> > boot sector info in a data segment and i write it "witha program " to
the
> > blank boot sector on a disk.... :)

>   In addition to writing the boot code to the boot sector of the floppy,
> and copying those files to the floppy, SYS.COM also makes sure that the
> location of the files on floppy is consistent with the only partial
> understanding of FAT12 present in the DOS boot code (is this still true
> in Win95? I'm not sure).  A boot sector with full understanding of a
> FAT12 FAT and root directory is easy to write, but last time I looked,
> MS hadn't.

>   So where were you planning to get the boot code from?  I can think
> of several possibilities, but I lost track of who originally asked
> what in this thread.

>   My PARTCOPY program (PCOPY??.ZIP on my web page) may be the easiest
> way to copy the boot code to a floppy.  It may also be the easiest way
> to copy boot code from a floppy or a partition on a hard drive.
> Use with care.  It is easier than debug or coding int13h calls, but
> don't let that give you a false sense that it is safer.

>   DOS used the same boot code on a FAT12 floppy as it used on a FAT16
> hard disk partition.  I think Win95 does too, but don't trust me.  If
> you have a bootable FAT16 hard disk partition, partcopy can read the
> boot code from it.
> --
> http://www.erols.com/johnfine/
> http://www.geocities.com/SiliconValley/Peaks/8600/



Mon, 15 Oct 2001 03:00:00 GMT  
 Making a boot disk without Sys.com

Quote:

>   In addition to writing the boot code to the boot sector of the floppy,
> and copying those files to the floppy, SYS.COM also makes sure that the
> location of the files on floppy is consistent with the only partial
> understanding of FAT12 present in the DOS boot code (is this still true
> in Win95? I'm not sure).  A boot sector with full understanding of a
> FAT12 FAT and root directory is easy to write, but last time I looked,
> MS hadn't.

Last time I looked (DOS v6.10), a floppy boot sector used the root
directory entries and FAT to find and load the system files. I'm not
sure if that was the first version to support this kind of loading,
though.

Quote:
>   DOS used the same boot code on a FAT12 floppy as it used on a FAT16
> hard disk partition.  I think Win95 does too, but don't trust me.  If
> you have a bootable FAT16 hard disk partition, partcopy can read the
> boot code from it.

As I said above, the boot code nowadays is different (different FAT
entry sizes that the code uses must be handled differently; previously
the system files were read from the beginning of the partition from
adjacent sectors, which is why it was not possible to move them around).
W95 with FAT32 uses different boot code (there are actually more than
one boot sector in FAT32, and the root directory can reside elsewhere
than at the beginning of the disk to make it able to grow if the number
of files in it gets too large).

        AriL
--
Humans may send email (if absolutely necessary) to the
obvious non-spam address.



Mon, 15 Oct 2001 03:00:00 GMT  
 Making a boot disk without Sys.com


Quote:

> > A boot sector with full understanding of a
> > FAT12 FAT and root directory is easy to write, but last time I looked,
> > MS hadn't.

> Last time I looked (DOS v6.10), a floppy boot sector used the root
> directory entries and FAT to find and load the system files. I'm not
> sure if that was the first version to support this kind of loading,
> though.

I suspect John refers to the way the MS boot sector code will only check
the first
two root entries for IO.SYS/MSDOS.SYS and not go through the entire root.

Quote:
> As I said above, the boot code nowadays is different (different FAT
> entry sizes that the code uses must be handled differently; previously
> the system files were read from the beginning of the partition from
> adjacent sectors, which is why it was not possible to move them around).
> W95 with FAT32 uses different boot code (there are actually more than
> one boot sector in FAT32, and the root directory can reside elsewhere
> than at the beginning of the disk to make it able to grow if the number
> of files in it gets too large).

It is only the FAT32 boot code which is "different". The FAT12/16 code is
still dumb. ;)

The FAT32 code uses 2 sectors for its code (Sector 0 & 2, sector 1 is the
FSINFO sector). BTW, the DOS directory entries have a fixed size of 32
bytes, but the LFN entries use *more than one* entry. Those extra entries
are "tagged" with attribute 0Fh, this stops older DOS versions from
"seeing"
them.

--
Regards,
TK - TBD



Tue, 16 Oct 2001 03:00:00 GMT  
 
 [ 9 post ] 

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