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From: ekalenda@cup.portal.com (Edward John Kalenda)
Newsgroups: comp.sys.tandy
Subject: Re: TANDY GRAPHIC DRIVER
Message-ID: <36134@cup.portal.com>
Date: 22 Nov 90 01:41:38 GMT
References: <11531@j.cc.purdue.edu> <6347@vice.ICO.TEK.COM>
  <11535@j.cc.purdue.edu> <6351@vice.ICO.TEK.COM>
Organization: The Portal System (TM)
Lines: 37

>>> The interrupt is the same set video mode interrupt that all of the other
>>> modes use : BIOS interrupt 16 (decimal), service 0 (AH = 0), with the
>>> required video mode in the AL register (the Tandy (PCJr) modes are 9 for
>>> 320 x 200 x 16 color, and 10 for 640 x 200 x 4 color).
>>
>>    These two modes are not really Tandy mode in which DESKMATE was written.
>> In the third mode, you can get 640 x 200 x 16.
>>
>  I don't think so.  I have never in all my wanderings through Tandy 
>  documentation, including the Tandy 1000 TX reference, found mention of
>  a 640x200x16 color mode.  This would require some 64k of video memory,
>  and I'm fairly sure that 32k is the max used by a 1000.
>
>  Feel free to prove me wrong, but if such a mode exists, it is totally
>  undocumented.
>
>  Bob Beauchaine
>  bobb@vice.ICO.TEK.COM	

In a game I ported from the Apple II/GS to the Tandy, I used mode E, the
640x200 16-color mode. There is no BIOS support for this mode, but the Tandy
1000 Technical Reference documents it fairly well. It starts at A000:0000,
uses one nibble per pixel, and is non-interlaced.

As a matter of fact, I used two nibbles for each pixel since the graphics
were all 320x200 and found that the same code for drawing into the VGA
mode 0x13 worked for Tandy mode E. Keep in mind that the CM-5 monitor does
not do 640x200, you need the CM-11 unless you do the pixel replication thing
that I did. There is a very disturbing waver on the CM-5 in the 640x200
mode.

If you have a truely pressing need to use this mode, I suppose I can excerpt
the code used to initialize the hardware and draw into it. Send e-mail to
the address below.

Ed
ekalenda@cup.portal.com