Browse Prior Art Database

Microcode Controlled Block Write for Graphics Buffer Fast Clear

IP.com Disclosure Number: IPCOM000122554D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 102K

Publishing Venue

IBM

Related People

Vanover, MT: AUTHOR [+2]

Abstract

This article describes a graphics VRAM buffer 'fast clear' algorithm. This algorithm uses the VRAM 'block write' feature on sufficiently large screen windows (areas to be updated), whereas it uses single pixel VRAM write for small windows as well as windows with unusual form factors. The result is performance optimization regardless of the window shape.

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This is the abbreviated version, containing approximately 52% of the total text.

Microcode Controlled Block Write for Graphics Buffer Fast Clear

      This article describes a graphics VRAM buffer 'fast
clear' algorithm.  This  algorithm uses the VRAM 'block write'
feature on sufficiently large screen windows (areas to be updated),
whereas it uses single pixel VRAM write for small windows as well as
windows with unusual form factors.  The result is performance
optimization regardless of the window shape.

      A functional capability of VRAMs called BLOCK WRITE is used in
which four consecutive memory locations are written with the same
data, using only one memory operation.  The advantage of this feature
is that the performance bandwidth is four times higher than normal
using this technique.  In practice, most windows consist of a portion
which matches the BLOCK WRITE address boundaries, as well as a
portion which does not.

      There are many applications which are addressed by this
technique as follows:
      . Fast clear (Initialize) of the Frame Buffer - This is useful
in both 2D and 3D applications, for both fixed frame and animation
cases.
      . Constant color fill of the Frame Buffer - This is useful for
cases where large areas need to be changed to a constant color value.
      . Fast clear (Initialize) of Z Buffer - This is useful in 3D
applications, for both fixed frame and animation cases.
      . Constant value fill of control plane buffers - Window ID
values are a good example of control planes.  BLOCK WRITE would be
useful in this case if a relatively large area of the screen were to
be assigned to a single window.

      In today's computer grap...