Browse Prior Art Database

Support of Multiple initial Microcode Load Images on Personal Computer Reference Diskettes

IP.com Disclosure Number: IPCOM000106157D
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 8 page(s) / 376K

Publishing Venue

IBM

Related People

Grimes, BR: AUTHOR [+2]

Abstract

Described is a firmware enhancement for reference diskettes, as used in personal computers (PCs) to support of multiple initial microcode load images (IMLs). A common reference between various PC models and sub-models is thereby provided. The concept enables each model's requirement to reflect different images in the support of IML images so that one common diskette can be provided to support a common diskette strategy.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 19% of the total text.

Support of Multiple initial Microcode Load Images on Personal Computer Reference Diskettes

      Described is a firmware enhancement for reference diskettes, as
used in personal computers (PCs) to support of multiple initial
microcode load images (IMLs).  A common reference between various PC
models and sub-models is thereby provided.  The concept enables each
model's requirement to reflect different images in the support of IML
images so that one common diskette can be provided to support a
common diskette strategy.

      In prior art, IML PC systems only supported a single power-on
system, test/basic input output system (POST/BIOS) image, on a
particular system's reference diskette.  This aspect limited the
reference diskette's capability to become a commonality among a
family of PC systems.  Without the ability to support multiple
POST/BIOS images from the reference diskette, a separate reference
diskette was required for each group of PC systems that use a
particular POST/BIOS image.  The concept described herein provides
the method needed to support multiple images thereby reducing the
number of multiple reference diskettes to one common diskette and to
support a common reference diskette strategy.

      Typically, PC systems require an IML such that loadable
firmware has become an enhancement to operational software.  In
certain models of PCs, the POST/BIOS firmware could be loaded from a
media source, such as a fixed disk or a diskette, into an area in
random access memory (RAM), commonly known as Shadow-RAM, and
executed as if it was running in the read only memory (ROM) address
space.  In this design, updating of the POST/BIOS firmware image
could be easily made without the need to upgrade ROM modules in the
system.  Software updates were able to be performed in the user's
location.

      In the IML operation, the POST/BIOS firmware image resides on a
local hardfile, or diskette, and is copied into the Shadow-RAM area
during the IML phase of the system POST.  During this phase, the IML
code attempts to load a master IML boot record into the system RAM
from the media source.  At this time, the IML code passes control to
the master IML boot record.

      Under normal conditions, the IML routine reads in the master
IML boot record from a fixed disk, or diskette whichever media is
selected, then transfers control to that media.  After the IML
routine loads the IML boot record into RAM, it jumps to the record's
starting address.  The master IML boot record verifies that the
associated firmware image is compatible with the system.  If the boot
record is compatible, the IML record loads the POST/BIOS firmware
image from the selected media into the Shadow-RAM and calculates the
checksum on the image.  If the checksum is valid, the master IML boot
record passes control to the POST/BIOS firmware image.  If the
firmware image is incompatible, or is invalid from the checksum, the
master IML record will gen...