Path: utzoo!mnetor!uunet!littlei!foobar!pmw
From: pmw@foobar.hf.intel.com (Pat Walsh)
Newsgroups: comp.graphics
Subject: Re: IBM PC Professional Graphics Adapter device driver
Message-ID: <160@foobar.hf.intel.com>
Date: 25 Mar 88 20:36:54 GMT
References: <25639@yale-celray.yale.UUCP>
Sender: news@foobar.hf.intel.com
Reply-To: pmw@foobar.UUCP (Pat Walsh)
Organization: - Intel Corp - Hawthorne Farms - Hillsboro, OR -
Lines: 26

The IBM PC Professional Graphics Adapter has several different flavors
of device driver depending upon your application.  Probably the most
well-known is called GSS-Drivers - this is the basis of the IBM VDI
product that was used when PGA was introduced.  CAD and Graphics Board
vendors have extended the original PGA instruction set and most applications
of any size that use PGA-style [i.e. non-shared-memory] interfaces include
their own 'driver' and 'CGI-like interface library' in the application.

CGA/EGA/VGA provide direct bitmap access to the host CPU and potentially
(actually) the application.  PGA provides a 'high level' command stream
interface and off-loads the interpretation.  Low-end systems tend to use
the shared memory architecture for cost reasons, and typically throw a
faster CPU at the problem if things slow down.  High-end systems tend to
use the non-shared memory (functionally partitioned) architecture to provide
dedicated computing resources for graphics operations.  As usual, IBM rode
the fence and introduced attempts at both architectures.  The primary
reasons PGA 'failed' in the PC were 1) cost advantage of EGA, 2) command
interface was not fast enough (bytes transfered vs. operations performed),
and 3) the interface was not flexible or 'rich' (text, line styles, etc)
enough for most applications.

Onwards to OS/2 Presentation Manager  :=)

-Patrick Walsh, (503)696-7216, Intel Corp; Hillsboro OR
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