On Friday, November 23, 2001, at 04:11  AM, Duane Maxwell wrote:

> Andrew C. Greenberg writes:
>> Here's the poop. From some old notes I found in my archives:
>
> This is more or less correct, though there are apparently some twists.  
> The
> most complete description I've found is:
>
> http://tarnover.dyndns.org/Documentation/Unsorted/Programming/hires.maps
>
> It talks about the funny ordering of bytes, the 
> blue/magenta/orange/green
> thing, and some little twist of  something odd happening every 14 
> columns,
> though I don't recall this from my days as an Apple ][ hack.

Nor do I.  I'm pretty sure this isn't right, otherwise assignments of 
byte pairs throughout the HIRES memory would appear screwy every 14 
columns -- and I don't recall anything like that.

> Of course, I've also downloaded the source to a few other emulators to 
> see
> how they handle it.  There's no question that it's a tough thing to do 
> both
> accurately and efficiently.  Many of them keep a copy of the current
> rendered image in addition to the normal memory map, and queue up 
> writes to
> be processed when they reach some threshold or the image is to be 
> painted on
> the display.  Another stategy that I like and may implement for lores 
> and
> text is to keep a list of dirty locations to make the display faster on
> redraw.

I was thinking along the same lines, and checked out the apple2-emulator 
for linux to that end.  I'm pleased to hear someone else is working on 
it -- I was about to sacrifice my productivity for the next month or so.

>> In practice, the trick for an Apple emulator isn't so much getting 
>> graphics
> to work
>> consistently, its sound and disk access.
>
> ...which are things I'm probably not going to waste any time on, though
> others are welcome to try.  My goal was to get the thing basically 
> working
> enough to run Applesoft correctly.  Why?  Beats me. Sometimes you just 
> gotta
> hack.

I suppose my job will be to pick it up from there until I can get Apple 
Pascal, and hence, Wizardry, to work.