Re: Apple II VGA Video Generator Card Project

["Michael J. Mahon" <mjmahon@aol.com>]

Mark McDougall wrote:

> Anyway, the point I was making is that the A2 graphics memory mapping, 
> even in ML, is going to make an impact on the speed of any graphics 
> routines on a 2MHz A2 - particular a brain-dead pixel-by-pixel 
> line-drawing algorithm.

I agree that linear addressing will make a positive difference,
and in the case of the slower BASIC routines, they may be rewritten
to get a significant speedup.  But in more general cases, like
animation, I doubt that it will make enough of a difference to
compensate for any sizeable increase in the number of pixels affected
in a graphics operation.  People have found many ways to mitigate the
apparent performance issues of non-linear addressing and bit-stuffing.

Before building anything, I recommend actually coding such routines
and assessing their performance for "enhanced" graphics modes to
determine the actual speed with which an unaccelerated Apple can
use such a mode.

They'll have to be coded anyway to make the mode(s) useful, so why not
code them and evaluate designs beforehand to guide design tradeoffs
and set realistic expectations for graphics performance?

-michael

Music synthesis for 8-bit Apple II's!
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