Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site watrose.UUCP
Path: utzoo!watmath!watrose!dmmartindale
From: dmmartindale@watrose.UUCP (Dave Martindale)
Newsgroups: net.micro
Subject: Re: Tandy 2000 color graphics - (nf)
Message-ID: <130@watrose.UUCP>
Date: Sun, 18-Dec-83 14:52:29 EST
Article-I.D.: watrose.130
Posted: Sun Dec 18 14:52:29 1983
Date-Received: Mon, 19-Dec-83 00:24:27 EST
References: <4566@uiucdcs.UUCP>
Organization: U of Waterloo, Ontario
Lines: 27

8 colours from a palette of 16?  Can you individually select which of the
16 colours the 8 possible pixel values map to?

Something is funny here.  If the video is separate RGB (and it would have
to be to get 640 pixels/line) and they used only 1-bit DACs (each of RGB
is either off or full on) you get only 8 possible colours.  2-bit DACs
give you 4 levels of intensity for each of RGB, and a total of 64 possible
colours.  If they already have more than 8 colours (implying the presence
of at least one DAC with more than 1 bit of input) and they have the ability
to map the 8 pixel values individually to one of a larger number of palette
colours (implying a colour lookup table) it is a real shame that they
simply didn't use three 2-bit DACs and a 6-bit lookup table, giving a palette
of 64 colours.  Going to 3-bit DACs would have allowed 8 distinct intensity
levels of grey (or any colour), allowing you to do reasonable antialiased
lines and characters, increasing the apparent resolution of the display.
The antialiasing could be done using any colour of lines on any colour
background (though you could only choose one foreground and background
colour for the whole screen), and the total palette would increase to
512 colours.  All of this without increasing the image memory at all,
just improving the video output hardware a bit.

Anyone know what they really did, and why they didn't go just a bit further?
I would guess that the additional hardware in the video output would be
cheap compared to the display memory.

	Dave Martindale
than 640x480