Browse Prior Art Database

Improved Z Buffer Clear Performance by Using the Test Mode Function of Dynamic Rams

IP.com Disclosure Number: IPCOM000101288D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Johnson, L: AUTHOR [+4]

Abstract

In two-dimensional (2D) graphics adapters, the need to quickly clear the contents of Frame Buffers and Window Buffers has been recognized by the manufacturers of VRAMs. Almost all have come up with methods to clear the memory faster than would be possible using normal random port writing modes. Two of these methods are commonly called Flash write and Block write. In three-dimensional (3D) graphics adapters, another buffer, usually called the Z buffer or Depth buffer, is required. This buffer is usually made of DRAMs since a serial output is not needed. Unfortunately, DRAMs do not have Flash write or Block write, which makes it difficult to clear a Z buffer quickly. This article proposes to use test mode to clear the Z buffer of a 3D graphics adapter faster than is presently possible.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 74% of the total text.

Improved Z Buffer Clear Performance by Using the Test Mode Function of Dynamic Rams

       In two-dimensional (2D) graphics adapters, the need to
quickly clear the contents of Frame Buffers and Window Buffers has
been recognized by the manufacturers of VRAMs. Almost all have come
up with methods to clear the memory faster than would be possible
using normal random port writing modes. Two of these methods are
commonly called Flash write and Block write. In three-dimensional
(3D) graphics adapters, another buffer, usually called the Z buffer
or Depth buffer, is required. This buffer is usually made of DRAMs
since a serial output is not needed. Unfortunately, DRAMs do not have
Flash write or Block write, which makes it difficult to clear a Z
buffer quickly. This article proposes to use test mode to clear the Z
buffer of a 3D graphics adapter faster than is presently possible.
The time in which the Z buffer can be cleared  is a major factor in
the performance of animation applications since the Z buffer must be
cleared before rendering each frame. As rendering speeds and
animation rates are improved, a fast Z buffer clear becomes even more
important.

      Example:

      If 1Mbit x 4 DRAMs are used, test mode is invoked by executing
the test mode set timings, which are shown in Fig. 1A.  After this is
done, the least significant column address becomes a "don't care"
state.  Both column address0 = 0 and column address0 = 1 will be
written simultaneously with th...