Path: utzoo!utgpu!watserv1!watdragon!dahlia!rsingh1
From: rsingh1@dahlia.waterloo.edu
Newsgroups: comp.sys.amiga
Subject: Re: Hi-res graphics ??
Message-ID: <19465@watdragon.waterloo.edu>
Date: 22 Dec 89 20:17:57 GMT
References: <2370@tukki.jyu.fi> <25260@cup.portal.com>
Sender: daemon@watdragon.waterloo.edu
Reply-To: rsingh1@dahlia.waterloo.edu ()
Organization: U. of Waterloo, Ontario
Lines: 50

In article <25260@cup.portal.com> LadyHawke@cup.portal.com (Classic - Concepts) writes:
>
>   The reason you are getting only 8 colors in high resolution instead of
>16 is probably because of memory limitations.  I have 2 meg (you mentioned
>1.5 meg), and that barely gets me the 16 colors.  With another 1/2 meg,
>your graphics programs will allow you the higher color modes.  With another
>meg, you would also be able to get Extra Half Bright (EHB) which would
>give you 16 colors plus 16 more in high resolution (640 x 400) of half
>intensity, with software which supports it such as DPaint III.  Try, the
>640 x 200 mode, with 1.5, I think you can get 16.  What other software
>are you using???                         J. Petersen (LadyHawke)

Sir, you do not understand of which you speak.

Even with a 512k un-expanded amiga 1000 I was able to view 768x480
images, and draw (in Dpaint 1 though), in 16 colours in high-res interlace.
 
The amiga, currently, has no more than 1024k of graphics memory available.
Most machines still have the old 'chip set' that give them 512k memory
for graphics.  All pictures, screens, windows, etc... must go into this
'chip' ram to be displayed.  640x400x16 colours requires only:
 640x400x4(bitplanes)/8(bits)/1024(bytes) = 125k ( I always thought it was
   128k? ? ?)... So, around 128k anyway.  My math may be wrong.
That's about 128k of graphics memory.  None of your expansion memory is
used for display-graphics.  It wouldn't matter if you had a billion
gigabytes of expansion ram, if you only had 100k of chip ram free (some might
be used up for windows, and screens and stuff), you couldn't display a
high-res 16 colour image.  That's the way it is.
 
Also, you are a bit wrong about Half Bright.  Half Bright only WORKS
in the 320ish accross-the-top modes. (The 'LoRes' modes).  Half Bright
does not work in high resolution.  Just like HAM mode does not function in the
high-resolution (640ish accross) modes.
 
To clear things up for you:
 
There are typicaly 2 types of memory for the amiga.  One is 'Chip' (graphics
ram.  It's called chip because it has to be 'attached' more or less directly
to the motherboard (so the custom chips can grab it when they like)).
The other, 'Fast' is ram that is not 'chip'.  The custom chips can not use
the 'Fast' Ram.  Fast Ram called 'fast' because it always runs full speed,
and does not get locked out when the custom chips do some wild stuff with
graphics memory.
 
Later

               /Paul Anton Sop (Esquire?).  rsingh1@dahila.waterloo.edu/
              /Graphic Designer 4 Spaghetti Western Words and Images  /
             /100 Kinzie Ave, Kitchener, Ontario, Canada, N2A 2J5    /
            /(519) 578-8525/742-0372 (if seriously really desparate)/