Subject: Re: Apple Internal Video
To: None <macbsd-general@NetBSD.ORG>
From: Henry B. Hotz <>
List: macbsd-general
Date: 02/16/1995 15:42:37
>Could someone tell me the Horizontal and vertical synch rates for the
>internal video on a Mac? Especially for a II ci?

The vertical rate is a bit over 66 Hz for anything driving the old standard
"high resolution RGB" monitor.  Don't know the horizontal.

If you don't mind my asking, why do you care?  What is the application?

>If I wanted to change from 640x480 to a higher resolution, just add more
>VRAM. Correct? What's the Max VRAM? Wouldn't the synch rates change?

On a IIci, wrong!  First of all on a IIci and IIsi the main DRAM is used
instead of VRAM.  Second of all the resolution is determined by the
available output clocks and the sense connections of the video cable.
(Issue #3 of Apple's Develop magazine covers the original scheme.  There is
probably a Tech Note that covers the extensions.)

There is a handy Init called MaxAppleZoom which will use the extra VRAM on
the old Apple NuBus video cards to fill in the big black border around the
edge (gives you 702 X 512 instead of 640 X 480).  I believe it works on a
IIci as well, but probably not any of the newer machines.  If you want to
increase resolution this is the prefered route---unless you can pay for a
new video card/monitor.  The latest version, 1.44, is known to work with
MacBSD.  (I used it myself on a IIcx!)

Henry B. Hotz

The opinions expressed are my own,
not Loral's, and not Librascope's.