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Browse Prior Art Database

Support in POST and SETUP for Automatically Setting Extra Video Memory

IP.com Disclosure Number: IPCOM000114692D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Le, KD: AUTHOR [+2]

Abstract

A software mechanism is disclosed that implements an automatic way of configuring added video memory (VRAM).

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

Support in POST and SETUP for Automatically Setting Extra Video Memory

      A software mechanism is disclosed that implements an automatic
way of configuring added video memory (VRAM).

      Current Micro Channel system customers have to run a setup
program when they change configuration.  With the technique described
in this article, video memory can be added to the system and it can
be automatically configured by a Power-On Self Test (POST).

      In systems that support a pre-defined amount of physical
memory, the video memory aperture (which can vary in size) can be
logically wired to start at a fit physical memory location.  By doing
this, the built-in video VRAM base address will never conflict with
other system memory.  Non-system memory must also be taken into
account whenever a system setup process is required.  This can be
handled by keeping required non-system memory information in
non-volatile memory (NVRAM), and taking that information into account
during the usual setup (configuration) process.

      POST hardcodes the VRAM aperture base address to the
pre-defined value then determines how much VRAM is installed.  The
datat then is saved to any hardware configuration register(s) that
require to be programmed.

      During a configuration (e.g., setup) process the configuration
program reads the hardware to determine how much VRAM is installed.
Two bits in NVRAM are set to reflect the amount of memory detected
during this setup process as follows:
  Bit 1-0 = 00  4MB VRAM present
            01  3MB VRAM present
            10  2MB VRAM present
            11  1MB VRAM present

       NVRAM bit definition (Byte)

Note:  More bits can be defined if needed to reflect amounts of video
mem...