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From: lphillips@lpami.wimsey.bc.ca (Larry Phillips)
Newsgroups: comp.sys.amiga
Subject: Re: amiga term flicker
Message-ID: <771@lpami.wimsey.bc.ca>
Date: 20 Sep 89 20:51:50 GMT
Lines: 43
Return-Path: <lpami!lphillips>
To: van-bc!rnews

In <5238@merlin.usc.edu>, aliu@castor.usc.edu (Terminal Entry) writes:
>What is the cause for the color flicker experienced with various amiga terminal
>programs such as JrComm, etc, when using ANSI color mode? Can it be fixed?
>It seems to me that the text gets scrolled a fraction of a second before its
>color gets scrolled.

The colour does not 'get scrolled' at all. the text you see on te screen (any
screen, any window), is the actual bitmap, ie. it is not scanned out from a
character generator each time the screen paints, as is the case with many
machines. Each colour you see on the screen is a direct result of which bits in
the bitplanes are on and which are off. The problem is that there is just not
enough time to scroll all the bitplanes during one vertical interval, so some
bitplanes are scrolled, and some are not when the raster comes by.

>I have experienced this problem at speeds of 2400, which should be more
>than slow-enough for the amy to handle. Yet, I haven't found a term that
>gives rock-solid 16-color ansi emulation yet. Is there such a thing?

It has nothing to do with the speed of the received data.

>(I always thought that is the c64/128 could do flawless 16-color scrolling, 
>the amiga should have no problem with it. Yet I find myself always in need 
>to adjust the color pallete on my terminal, or not use color at all..)

Well, the 64/128 do it completely differently. They use a text buffer (contents
in ASCII, and a colour table the same size as the text buffer (size is equal to
the number of characters that can display on the screen), and there is not
nearly as much data to scroll as there is on the Amiga display.

If you feel strongly about it, let Jack know, and perhaps he'll put in an
option for allowing double buffering of the display. It will eat a lot of ram,
and may have other problems though.

-larry


--
The Mac? Oh, that's just like a computer, only slower.
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|   //   Larry Phillips                                                 |
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