Re: Mockingboard output through IIgs internal speaker?

[mjmahon@aol.com (Michael J. Mahon)]

Charlie wrote:

>"Roger Johnstone" <roger@ihug.invalid> wrote in message
>20031215193734463+1300@news.inv.ihug.co.nz">news:20031215193734463+1300@news.inv.ihug.co.nz...
>> In <bri3lp01oso@enews1.newsguy.com> Charlie wrote:
>> >
>> > I've always wondered why the "monochrome" display setting only worked
>> > for Double HiRes when using an RGB monitor.
>> >
>> > Charlie
>>
>> Because double hi-res really has two modes: 560 pixels per line in
>> monochrome and 140 pixels per line in colour. The older computers had no
>> way of telling which mode you wanted, so the IIe composite colour
>> monitor has a switch on the front to turn off colour! The IIgs replaces
>> that with a softswitch. Some IIgs-aware programs which use DHR graphics
>> will automatically change the setting themselves e.g. IIRC PublishIt!
>> uses DHR and will switch a IIgs to monochrome while it's running.
>
>Thanks for the information.  I had always thought that DHR graphics had only
>one mode (140 pixel color) and that the composite color monitor switch just
>turned off the color burst signal.

The switch on the monitor _does_ simply kill the color decoding.

For any 8-bit Apple (non-IIgs) with DHR, the only difference between
140 16-color pixels and 560 monochrome pixels is how the monitor
interprets the video signal.  If the 8-bit Apples could disable the color
burst for graphics modes, then they could control that interpretation.

The colors on a composite monitor result from chroma decoding of
four monochrome pixels, and are sometimes known as artifact colors.
(The design of the Apple II graphics system is based on artifact
colors.)

-michael

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