[stella] slightly offtopic: Apple II mouse pointer in vblank?

Subject: [stella] slightly offtopic: Apple II mouse pointer in vblank?
From: KirkIsrael@xxxxxxxxxxxxx
Date: 28 Jan 2004 02:09:28 -0000
For some reason the lore and hardware of the early Mac has 
always fascinated me, so I'm greatly enjoying the site
http://folklore.org/ (I'm reading through it, but each page
is slow to load, so I end up shift-clicking on the next page
to effectively precache...works pretty well)

Anyway, this page describes a hacky project to get a mouse pointer
working on a "humble" Apple II:


(or click http://tinyurl.com/3dsuq )

It says 
To move the mouse cursor without flickering, both the Mac and the Apple III code used a vertical blanking interrupt, which drew the cursor during the time interval when no video was being painted.

(and then goes on to explain some clever hackery to do the same on
Apple II, which didn't have a proper vertical blank interrupt)

But, given my experience w/ the 2600, I don't understand how you 
draw *anything* during VBLANK...almost by definition! 

Anyone know what they mean, and how it would relate to my experience
on the 2600?

That's a great site, btw.

KirkIsrael@xxxxxxxxxxxxx    http://kisrael.com
DEFEAT "For every winner, there are dozens of losers. 
          Odds are you're one of them." --Demotivators, http://despair.com

Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/

Current Thread