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From: sands@apple.com (Michael Sands)
Newsgroups: comp.sys.mac.hardware
Subject: Answers to new Display Cards
Message-ID: <7420@goofy.Apple.COM>
Date: 28 Mar 90 01:05:35 GMT
Sender: usenet@Apple.COM
Organization: Apple Computer, Inc.
Lines: 39


There is an upgrade from the Macintosh Display Card 4(dot)8 to the 8*24.  
You buy additional memory and plug it into the SIMM sockets.  This upgrade 
is one meg of VRAM.

The Macintosh Display Card 8*24 GC (what a mouthfull!) cannot be created 
out of the plain 8*24 card.  The graphics accelerator uses the AMD 29000 
general risc processor to gain acceleration over the other frame buffer 
cards.  

All these cards drive all monitors currently available from Apple.  They 
plug and play.  They are also capable of NTSC output and Apple's 
convolution, a method of reducing flicker on interleaved displays.  The 
NTSC is color if you use a video conversion box.

The 8*24 GC is capable of master block transfers on the NuBus and it uses 
this function to accelerate the QuickDraw rendering on other framebuffer 
cards plugged into the NuBus slots.  These other cards need to be capable 
of slave block transfers.  The Mac IIci's framebuffer is not on NuBus
but it is accelerated. 

It should be noted that the acceleration in all these cases is not 
consistent and varies according to the bit depth, QuickDraw calls being 
used, CPU, and other cards in the NuBus slots.  Some of the applications 
do not use the off screen bit map support offered originally with the 
introduction of 32-bit QuickDraw.  These features were placed there deliberately in anticipation of the graphics accelerator.  Some applications will therefore not run as fast as they could.  It is important to note that everything is accelerated.

An often forgotten result of using the graphics accelerator is the 
additional time the Mac now has to do processing, once relieved of having 
to do the graphics.  Not only do the graphics go faster, but the 
applications fly as well!  Isn't it wonderful what parallel processing can 
do?



Michael Sands
system extension group
(408) 974-6108
novice driver, just my thoughts