[GOODIE] A2Emulator

Andrew C. Greenberg werdna at mucow.com
Fri Nov 23 09:01:28 UTC 2001


It always worked for me.

On Friday, November 23, 2001, at 03:04  AM, David Harris wrote:

> I don't remember all the details, but there was some reason why that 
> was not
> the way to do it -- maybe memory?  I probably have the 
> code....somewhere ;-)
>
> David
>
> "Andrew C. Greenberg" wrote:
>
>> On Thursday, November 22, 2001, at 09:30  PM, David P. Harris wrote:
>>
>>> I wrote a 4x8 character display routine in assembler for the Apple II
>>> for Forth, so we could get a reasonable char/line.  It worked ok, but
>>> had to use a lot of tricks and that addressing is mighty messy!  A lot
>>> of work to cram the bits into the display memory.
>>
>> Well, in practice all you do is build a table of offsets, load the
>> y-offset into the index register and use an indexed indirect mode to 
>> get
>> to the correct byte.  The trick is making whatever you want to look
>> good, because of the peculiarities in the color map.





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