Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!killer!ames!oliveb!amiga!jimm
From: jimm@amiga.UUCP (Jim Mackraz)
Newsgroups: comp.sys.amiga
Subject: Re: Silver (was Re: Amiga 2000 has been swapped)
Message-ID: <2817@amiga.UUCP>
Date: 28 Aug 88 22:11:39 GMT
References: <2@orbit.UUCP> <6908@well.UUCP> <786@applix.UUCP> <2572@sugar.uu.net>
Reply-To: jimm@cloyd.UUCP (Jim Mackraz)
Organization: Commodore-Amiga Inc, Los Gatos CA
Lines: 33

In article <2572@sugar.uu.net> peter@sugar.uu.net (Peter da Silva) writes:
)In article <786@applix.UUCP>, scott@applix.UUCP (Scott Evernden) writes:
)> The standard VGA measures 640 x 480, or less than 40k.  It is true that
)> there are multiple bit planes, but they all live at the same address.
)> To read from an individual plane, you tell a register which one you want and
)> read.
)
)This is, of course, bank selecting. Which is about the only thing worse
)than an intel segmented architecture (which amounts to bank selecting on
)chip).

It's a little more than that.  You select things akin to "pen colors"
and a single write can affect ALL planes, setting 0's in some, 1's in
others.  EGA, at least, come up an inch short of being able to set
arbitrary foreground and background pens for a dashed line, for example,
due to bad thinking in the register conventions (I got a long letter
about this printed in Programmers' Journal, mostly rehashing an observation
of Neil Katin).  But it's better than bank selecting, and smells kind of
like the kind of thing you'd want to do for a parallel Amiga blitter,
if you were building one: separate minterms per bitplane.

)You'd do better with segments.

But, Peter, you get to be burned by BOTH at once!!

)		Peter da Silva  `-_-'  peter@sugar.uu.net

    jimm
-- 
	Jim Mackraz, I and I Computing	  
	amiga!jimm	BIX:jmackraz
Opinions are my own.  Comments regarding the Amiga operating system, and
all others, are not to be taken as Commodore official policy.