Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

BIOS Function Call to Set Model Byte

IP.com Disclosure Number: IPCOM000105947D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Agoglia, RJ: AUTHOR [+4]

Abstract

Disclosed is a modification to a BIOS routine in a computing system to include a function call for setting the model byte when the system is running with ROM mapped to RAM. In this way, the system can have a two types of model bytes in ROM, one of which is initially mapped to a RAM address and the other of which is set in this address with the function call.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

BIOS Function Call to Set Model Byte

      Disclosed is a modification to a BIOS routine in a computing
system to include a function call for setting the model byte when the
system is running with ROM mapped to RAM.  In this way, the system
can have a two types of model bytes in ROM, one of which is initially
mapped to a RAM address and the other of which is set in this address
with the function call.

      The model byte of ROM BIOS is used by various application
programs to vary the execution of code in accordance with the model
or type of system.  For example, a model byte with a hexadecimal
value of FC indicates that a system has a 80286 processor, while a
model byte with a hexadecimal value of F8 indicates that a system has
an 80386 processor.  A problem with the use of a single model byte in
this way occurs when a single processor is used is systems having two
types of bus architectures, such as the AT bus and the Micro Channel*
bus.  In this case, if an application program assumes the wrong type
of bus architecture, the application may operate incorrectly or hang
up the system.

      The first model byte from ROM is preferably loaded into a
memory address with the value of FFFF:E when ROM is mapped into RAM.
Thus, the system can run applications developed for systems using
BIOS routines without this function call.  Then, during the execution
of BIOS, a "Set Model Byte" function call causes this address to be
rewritten with a new model byte and to u...