Browse Prior Art Database

Frame Buffer Data Used as RamDac Commands

IP.com Disclosure Number: IPCOM000114998D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 83K

Publishing Venue

IBM

Related People

Lawless, WF: AUTHOR

Abstract

In today's graphics designs, X-Windows allows a user to have many different windows and types of windows on the screen at the same time. Window types can be 4 Bit Per Pixel, 8 Bits Per Pixel, 8 Bit Per Pixel Double Buffer, possibly 16 Bits Per Pixel, and others. Each pixel type or pixel interpretation can be in separate windows displayed on the screen at the same time. Today's designs use Window IDs scanned into RamDacs along with the pixels to describe that Pixels Type. If 4 Pixel Types are used then each pixel needs 2 Bits to describe its Pixel Type, and more Bits if a separate Look-Up-Tables are used. If 16 Pixel Types are used then 4 Bits are needed and so on.

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Frame Buffer Data Used as RamDac Commands

      In today's graphics designs, X-Windows allows a user to have
many different windows and types of windows on the screen at the same
time.  Window types can be 4 Bit Per Pixel, 8 Bits Per Pixel, 8 Bit
Per Pixel Double Buffer, possibly 16 Bits Per Pixel, and others.
Each pixel type or pixel interpretation can be in separate windows
displayed on the screen at the same time.  Today's designs use Window
IDs scanned into RamDacs along with the pixels to describe that
Pixels Type.  If 4 Pixel Types are used then each pixel needs 2 Bits
to describe its Pixel Type, and more Bits if a separate
Look-Up-Tables are used.  If 16 Pixel Types are used then 4 Bits are
needed and so on.  This number of Bits is multiplied by the number of
pixels scanned in to the RamDac and could equal 16 or 20 pins extra
Hardware Pins not to mention the extra memory to do this.

      This paper will show how to hide pixel interpretations and
RamDac Commands behind the Motif Border for X-Window or windows
systems.  Using one Bit Per Pixel extra it can achieve up to 256
different Pixel Types and RamDac Commands Combine.  Commands such as
Change values in the Look-Up-Table or change pixel type from 8 bits
to 24 bits can be executed using this method.  For example, the
entire Look-Up-Table can be changed by scanning commands out during
Vertical Sync (Blank) and loaded at dot clock speeds instead of
load/store cycles.

      One Bit To Execute RamDac Commands - Frame Buffers should be
organized as such.  For ease of drawing 2 meg VRAM chip (512 X 512 x
8)
are used to create a 1280 x 1024 screen size.

      How It Works - One Bit Per Pixel is scanned into the RamDac
along with pixel data from the Frame Buffer.  If this b...