Browse Prior Art Database

Fast DOS Soft Boot

IP.com Disclosure Number: IPCOM000111323D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

Chen, F: AUTHOR

Abstract

In a Disk Operating System (DOS) a very fast DOS soft boot is provided by restoring the DOS image from extended memory, which was previously, preferably, compressed and saved after system initialization, thereby eliminating overhead from a disketter or disk.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Fast DOS Soft Boot

      In a Disk Operating System (DOS) a very fast DOS soft boot is
provided by restoring the DOS image from extended memory, which was
previously, preferably, compressed and saved after system
initialization, thereby eliminating overhead from a disketter or
disk.

      Important aspects of the DOS programming environment are their
simplicity and openness.  Programs that run in real mode can do many
things as long as they know where and how, e.g., hooking the
interrupt, peeking and poking the DOS system variables, replacing the
system services with private routines, etc.  This open relationship
makes DOS appealing to programmers, providing many applications and
system extensions.  However, the price paid for this strength is the
risk of bringing the system down.  Mistakes made by the running
programs can hang the system.  In the software development
environment, this situation occurs quite freuently.  Unfortunately,
bringing the system back from either diskette or disk can take a
relatively long period of time.  This article provides a solution
that can restore the system almost instantaneously.

      The solution is based primarily on the assumption that programs
which hang the system do not change or destroy the saved system image
in extended memory.  This assumption is quite reasonable because DOS
programs run in real mode and the normal wy to access extended memory
is through the protect mode gateway provided by extended memory
services (XMS) and DOS extender services, such as DOS protected mode
interface (DPMI) which are mostly bug-free and provide well protected
memory regions.  The primary design of this solution is distributed
in the following areas:

1.  A utility program is used to compress the DOS system memory image
    from memory location 0:0 to the starting address of the utility
    program and to save it in extended memory.  To ensure the
    correctness of the image, the following information must be
    saved: checksum of the image, length of...