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From: valthoff@magnus.acs.ohio-state.edu (Victoria M Althoff)
Newsgroups: comp.sys.apple2.programmer
Subject: Re: Hi-res Graphics
Date: 12 Oct 1993 03:41:52 GMT
Organization: The Ohio State University
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Message-ID: <29d920$gqs@charm.magnus.acs.ohio-state.edu>
References: <29apmh$der@charm.magnus.acs.ohio-state.edu>
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Summary: Part Two:  Double Hi-Res
Disclaimer:  "Apple" is a registered tm. of You-Know-Who.

Okay, so I talked about hires graphics.  Now, about Double Hi-Res Graphics.

First, you need a ][e or later; a ][e must NOT have a Rev. A motherboard.  You 
also need at least 128k.  Furthermore, simply sticking one of those big Apple 
memory cards into a 64k ][e won't do it...you MUST have 64k on the 80-column 
card in the auxiliary slot.  And, the jumper on the two pins on the end of the 
card must be installed.  If you have one of the later E's (including all of the
grey ones with the numeric keypads) with the miniature 80-column card, there is
no jumper.

1.  How do you activate DHR?
First, activate the 80-column card (yes, that's "PR#3").
Then, enter high-resolution graphics (uh huh..."HGR").
Now, the procedure differs from that listed in official Apple publications, 
which instruct you to turn the paddle port Annunciator #3 "on".  This is 
rubbish.  Instead, you turn it OFF by accessing location 49247 (sorry, I'm not 
sure what that is in $hex).

2.  What is the pixel set/reset protocol?
Same as for HGR.  I'm not sure exactly how the colors are mapped, though, since
the 560 x 192 mode is supposed to offer 15 colors.

Okay, here's where it gets tough.  The DHR screen is 80 bytes wide, but those 
80 bytes only occupy 40 addresses.  The first byte and second byte BOTH have 
the addess $2000.  But the first byte is in 'aux' (80-column card) memory, and 
the second is in normal memory.  The bytes continue to alternate like that all 
the way across the screen.
To make things more difficult, the Applesoft hires graphics commands completely
ignore the extra screen pixels, so any normal hi-res Applesoft program running 
in DHR will leave unsightly gaps.  Also, there is no second hires page in DHR.

Getting results takes some page flipping,which I don't have time to discuss 
here.  But you get the general idea.

--Dave Althoff, Jr.
(Maybe I'll come back to this...)