Path: utzoo!utgpu!news-server.csri.toronto.edu!eecg.toronto.edu!leblanc
Newsgroups: comp.sys.amiga
From: leblanc@eecg.toronto.edu (Marcel LeBlanc)
Subject: Re: Cheesy Amiga Video
Message-ID: <1990Sep4.224321.3797@jarvis.csri.toronto.edu>
References: <9714@scorn.sco.COM>
Distribution: na
Date: 5 Sep 90 02:43:21 GMT
Lines: 51

allanh@sco.COM (Boy Howdy) writes:

>...So I was pawing through the June 1990 issue of AmigaWorld, trying to
>find out what the A3000's built-in video capabilities are, when I
...
>And, later on page 32:

>   "The new higher-resolution ECS modes actually have fewer colors than
>   standard modes.  Because only a limited amount of display information
>   can be sent out the video port, a noninterlaced screen can be
>   achieved only by dropping the maximum number of colors to four from a
>   palette of 64.  Even at four colors, these modes put such a large
>   burden on system resources that they may cause problems for some
>   programs.  For everyday use, you will probably want to run the
>   640x480 noninterlaced mode on a black-and-white screen."

I think you've missed several important points.  The most important one may
be that the A3000 includes a built-in de-interlacer circuit.  This means
that video modes of 640x400+ and 640x512+ (or even 640x480) that were
interlaced on the A500 and A2000 are now automatically de-interlaced at NO
MEMORY BANDWIDTH COST.  The output from the de-interlacer goes to a separate
VGA-style port.  The 640x480 productivity mode that the article discusses is
a special mode that does not require the de-interlacer.  This mode really
isn't needed on the A3000.  Productivity mode is mainly intended for the
A2000 and A500, which will eventually use the same video chips (but won't
have a de-interlacer).

Also, you're making several assumptions about facts that aren't stated in the
article.  All IBM display cards include their own memory on-card for video
displays, because the ISA bus couldn't possibly handle the bandwidth needed
to display video.  This means that on clones you pay for video memory that
can't be used for anything other than video (e.g. it can't be used to run
software).  On all Amigas, the video memory CAN be used for other things.
If you only have 512K of video RAM (and nothing else), then you can use
video memory (CHIP RAM) to run software.  On clones, YOU DON'T HAVE THIS
OPTION!  Most Amigas are equipped with Fast RAM.  Fast RAM is always used if
it is present!  When you are using Fast RAM, the processor (68000 OR 68030)
is not slowed down BY ANY VIDEO MODES!!!  Not even by productivity mode!

Don't let the clone dweebs confuse video issues with misleading facts.
Amigas make use of the advantages of having the video system tightly coupled
with the CPU.  Clones make use of the advantages of *NOT* having the video
system tightly coupled with the CPU.  Both approaches have advantages and
disadvantages.

>Allan J. Heim / ...!uunet!sco!allanh / allanh@sco.COM
>voice: +1 408 425 7222 x6343 / fax: +1 408 429 1887

Marcel A. LeBlanc  --  Electrical Engg Computer Group, Univ. of Toronto
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