Browse Prior Art Database

Extending Personal System's Selection

IP.com Disclosure Number: IPCOM000099202D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Bealkowski, R: AUTHOR [+2]

Abstract

A technique is described whereby the video color can be extended from 256 colors to over 16 million choices through the use of an indirect index table and circuitry.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 62% of the total text.

Extending Personal System's Selection

       A technique is described whereby the video color can be
extended from 256 colors to over 16 million choices through the use
of an indirect index table and circuitry.

      Generally, a personal system, such as the IBM PS/2, is with a
video subsystem with the capability of up to 256 colors
simultaneously.  Typically, a converter (DAC) is used and is equipped
256 data registers, containing eighteen bits each, to the display of
up to 256 colors from a possible 256K  Each 18-bit register has six
bits each for red, and blue.  The data registers are programmable
from host.  The video DAC is responsible for converting information
from video memory into analog signals to used by the video display.
The concept herein extends the video architecture so as provide the
ability to support 16,777,216 color choices.

      The drawing illustrates the use of indirect index table 10
which allows an eight-bit input index to select a value. The 24-bit
DAC 11 provides the ability to up to 16M colors.  In compatible modes
of operation, eight-bit video color value is used as an index into
IIT  This eight-bit index selects a single 24-bit IIT entry be used
as input to the DAC.  The programming of the IIT the 24-bit output
value and, therefore, the color by the eight-bit index.  The old
18-bit value can be represented in the new 24-bit field of the IIT.

      To extend compatible modes of operation, the programming the
IIT is p...