Browse Prior Art Database

Method of Expanding the Hardware of a Personal Computer With Minimal Impact to Software Drivers

IP.com Disclosure Number: IPCOM000099221D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 2 page(s) / 97K

Publishing Venue

IBM

Related People

Piazza, WJ: AUTHOR

Abstract

This article describes a method of expanding the capabilities of a personal computer (PC) system causing the software drivers (i.e., BIOS) to be rewritten or duplicated in memory.

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

Method of Expanding the Hardware of a Personal Computer With Minimal Impact to Software Drivers

       This article describes a method of expanding the
capabilities of a personal computer (PC) system causing the software
drivers (i.e., BIOS) to be rewritten or duplicated in memory.

      Some current point-of-sale terminals (POSTs) attach to a PC
through the serial and parallel ports, keyboard, and ports of the
system.  It is desired to architect an card which will occupy one
slot in the host PC will allow the connection of another POST to the
PC.

      Selecting addresses for the keyboard and serial and ports is
not a substantial problem, since these use only a half dozen or so
I/O addresses and no addresses.  In the case of he serial and
parallel the base address is stored in a table in memory so it can be
easily changed.

      The video port poses special problems, however.  First,
requires a fairly large block of video memory addresses. the BIOS
software which drives the video hardware is structured to allow for
the selection of multiple video at various addresses.  Even if it
were possible to the hardware problem by simply duplicating the video
at a different set of addresses, the software would have to be
substantially rewritten or duplicated in with all appropriate
addresses changed.

      In the method disclosed herein, the video circuitry at standard
video I/O and memory addresses is implemented a standard color/
graphics adapter (CGA) to provide a that allows the selection of a
single attachment from among two or more.  A small amount of
additional allows the selection of the card, and, once the unmodified
BIOS software works with that card. components of the card which
allow this to be done are in the drawing.  Each POST attachment card
contains switches 1 which assign each card to a unique "address" the
system.  Also, located on each card is a "write register" 2.  The
address of this register is decoded signals on the system address and
control bus 3 by the decoder 4 to produce a signal 5 which cau...