Re: Implement Double-Res Differently

[Jeff Blakeney <CUTjblakeney@sentex.net>]

On 14 Jan 2003 10:48:26 -0800, steve@dosius.zzn.com (Dosius) wrote:

>Holger Picker <pickerh@uni-muenster.de> wrote in message news:<Pine.A41.4.44.0301141023030.104236-100000@zivunix.uni-muenster.de>...
>> On Mon, 13 Jan 2003, Bryan Parkoff wrote:
>> 
>>> Date: Mon, 13 Jan 2003 22:53:02 -0600
>>> From: Bryan Parkoff <BParkoff@satx.rr.com>
>>>
>>>     I know the fact is that 40x24, 80x24, low resolution, and high
>>> resolution use 280x192 pixel, but double resolution uses 560x192.  Is it
>>> true that one pixel plots in the screen using both main and aux memory page.

Actually 80x24 text uses a resolution of 560x192.  This is why you
can't normally get 80 column text without having at least an 80 column
card installed in your Apple II.  It is possible to get 80x24 text or
even 560x192 resolution graphics using just the standard HR screen but
there are some limitations, you have to be very careful about how you
set the pixels and you have to use a monochrome screen.  However, to
emulate this you still need to emulate a 560x192 resolution to
reproduce it.

>>> I love to use 320x280 pixel on all PCs that look like real 560x192 pixel.
>>
>> What do you mean by that? How can 320x280 look like "real" 560x192?
>> (Which standard PC screen mode do you use for a resolution of 320x280?)
>
>Could he mean 320x200? ... Still, you can't do 560x192 in 320x200.

The 320x200 mode of video cards could be manually manipulated to
generate a few other resolutions.  It was a pretty common trick.  I
don't think you could get 320x280 but I know you could get 320x200,
320x240, 320x400, 320x480, 360x200, 360x240, 360x400 and 360x400.

>>> Both main and aux memory pages will map into single memory to form
>>> one pixel using 280x192 resolution on 320x280 resolution that will look
>>> much nicer. What do you think about my idea?
>>
>> Are you sure that it will look nicer? AFAIK, most of the programs I know of
>> so far do expect a resolution of 560x192, otherwise they won't work. For
>> example, have a look at the game "Pirates". The characters on screen become
>> totally illegible when seen under a resolution less than 560x192. Other
>> examples would be "Test Drive", or "Dragon Wars" (i.e. every program that
>> writes characters to the screen).
>
>Obviously Dapple 1.25 (using 140x192 over 320x200) will show this
>clearly.  Zork Zero is another example.

That would probably be okay for doing a colour DHR screen because even
viewing characters on a composite colour monitor you get colour
bleeding in the characters themselves so they never look like they are
using a 560x192 resolution.  This is why there are usually only 40
characters per line on a DHR screen.  To make it so you can still read
the characters through the colour bleeding.

However, converting a DHR screen to 140x192 on a 320x200 screen will
only work when dealing with a colour DHR screen.  If you need to do a
monochrome DHR screen for something like that Strar Trek: The Next
Generation game, this would come out looking pretty awful.  Monochrome
DHR requires at least 560x192 resolution so is best handled by a
resolution of 640x400 at the least.

-- 
 Jeff Blakeney - Dean of the Apple II University in the
                 Apple II Community on Syndicomm.com
 CUT the obvious from my address if you want to e-mail me