Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!husc6!rutgers!rochester!pt.cs.cmu.edu!andrew.cmu.edu!mp1u+
From: mp1u+@andrew.cmu.edu (Michael Portuesi)
Newsgroups: comp.sys.amiga
Subject: EGA/VGA (was Re: Silver (was Re: Amiga 2000 has been swapped))
Message-ID: 
Date: 18 Sep 88 21:55:33 GMT
References: <2@orbit.UUCP> <6908@well.UUCP>,
	<786@applix.UUCP>
Organization: Carnegie Mellon
Lines: 20
In-Reply-To: <786@applix.UUCP>

> *Excerpts from ext.nn.comp.sys.amiga: 25-Aug-88 Re: Silver (was Re: Amiga*
> *2.. Scott Evernden@applix.UU (1883)*

> Anyways, the killer with EGAs/VGAs, is that you _have_ to get down and dirty
> with the IO registers to accomplish any real work.  This is quite a painful
> process on the non-memory-mapped-IO 80x8x's.  You repeatedly play games like:
> mov dx,SEQ_ADDR; mov al,WPL_REG; out dx,al; inc dx; mov al,1; out dx,al).
> Registers are pretty much lost, like DX, for this- on an architecture that is
> already register-starved.

The way the problem with VGA was explained to me, it is possible to memory map
the *first* bitplane of display.  Accessing any further bitplanes require the
bogus gymnastics detailed above.

                        --M

Michael Portuesi / Information Technology Center / Carnegie Mellon University
ARPA/UUCP: mp1u+@andrew.cmu.edu                     BITNET: rainwalker@drycas

"if you ain't ill it'll fix your car"