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Method to Boot Multiple Diskette Images from a CD

IP.com Disclosure Number: IPCOM000114414D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Bennett, CA: AUTHOR [+2]

Abstract

Operating Systems are becoming increasingly large. Due to this there is a need to be able to boot from multiple diskettes (currently OS/2* requires two diskettes to boot). The current boot methods from CDROM only allow for booting from one diskette image. This method allows for booting from multiple images.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 54% of the total text.

Method to Boot Multiple Diskette Images from a CD

      Operating Systems are becoming increasingly large.  Due to this
there is a need to be able to boot from multiple diskettes (currently
OS/2* requires two diskettes to boot).  The current boot methods from
CDROM only allow for booting from one diskette image.  This method
allows for booting from multiple images.

      Some operating systems exist today that need more than one
diskette to boot their minimal system (e.g., OS/2), and there is a
good chance that many more will follow this trend.  Booting from CDs
is becoming more and more a standard.  There is a method of booting
floppy images from CD; however, today there exist only a method of
booting one floppy image from CD.  This method allows booting from
multiple diskette images residing on a CD.  This was implemented in
OS/2, but this code could be easily ported to any OS.

Essentially this was achieved in the following manner:
  1.  Retrieve value of placement of first bootable image from
       Extended BIOS Data Area (EBDA)
  2.  Subtract physical size of floppy image from that value (the
       result is the location of the second floppy image needed to
       boot).
  3.  Write this value back out to EBDA
  4.  Repeat steps 1 and 2 if more floppy images are needed to boot.

       Note: This method assumes that the bootable floppy images are
written to the CD in inverse order in which they are needed to boot
(i.e., i...