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

Subject: Re: [stella] slightly offtopic: Apple II mouse pointer in vblank?
From: "B. Watson" <atari@xxxxxxxxxxxxxx>
Date: Tue, 27 Jan 2004 21:56:27 -0500 (EST)

On Tue, 28 Jan 2004 KirkIsrael@xxxxxxxxxxxxx wrote:

> Just a thought...could they mean "draw the cursor" to video memory
> or something like that, as opposed to the literal video signal? That
> occured to me after I sent this...

Yep. The Apple II has a framebuffer (video RAM), so you could draw into
RAM which the graphics hardware will display when it gets around to
drawing the frame.

All the late 70's/early 80's home computers that I know of had video RAM
and hardware that read the RAM and drew the frame.. the 2600 technique of
following the TV beam in real time was pretty rare, though still possible,
you could e.g. disable the ANTIC chip on an Atari 800 and treat the GTIA
the same way you treat the TIA on a 2600. Some (most? a few? dunno)
games did this (Pitfall II for the 800 did), but other apps generally
didn't need to.

In a way the ANTIC and (Commodore) VIC-II chips were the primitive
ancestors of today's 3D cards, I guess you could say. They used hardware
to render frames so you didn't have to in software.

Hm, anyone who knows, what other machines (consoles or computers) back
then used the per-scanline style of drawing a frame? The 2600 can't be
the only one...

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