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Browse Prior Art Database

Using VRAM for a Fast Read/Modify/Write

IP.com Disclosure Number: IPCOM000119730D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 49K

Publishing Venue

IBM

Related People

Albaugh, VA: AUTHOR [+2]

Abstract

Disclosed is a method of using VRAM (Video Random Access Memory) to improve the throughput of a Z-buffered graphics adapter performing the function of surface shading.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 63% of the total text.

Using VRAM for a Fast Read/Modify/Write

      Disclosed is a method of using VRAM (Video Random Access
Memory) to improve the throughput of a Z-buffered graphics adapter
performing the function of surface shading.

      The design consists of 2 basic elements:
           1) A custom logic chip that contains the color
     interpolation, Z comparison logic, output to a display
      buffer, and pipelining to achieve the desired
      throughput.
           2) A memory device to hold the Z values.  This is
      implemented with a dual-ported VRAM.  The serial port
      is used to read the Z values sequentially.  The
      parallel port is used to write back the results of the
      comparison of old Z values with the Z values generated
      by the custom chip.

      For each scan line for which potentially new shading is
available from the custom chip, the following operations occur:
           1) A word of the appropriate existing Z values is
      read from the VRAM via the serial port.
           2) The custom chip generates interpolated Z values
      for each associated x,y pixel position as well as the
      corresponding color value.
           3) Within the custom chip the existing Z values
      are compared to the new values.  If a new value of Z is
      less than the associated existing value, then the
      display buffer is...