Path: utzoo!attcan!uunet!know!zaphod.mps.ohio-state.edu!ub!dsinc!bagate!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: Some MAC and Amiga Comparisons.
Message-ID: <15323@cbmvax.commodore.com>
Date: 22 Oct 90 20:48:53 GMT
References: <33538@nigel.ee.udel.edu> <11388@life.ai.mit.edu> <84888@tut.cis.ohio-state.edu> <11419@life.ai.mit.edu> <16885@thorin.cs.unc.edu>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 35

In article <16885@thorin.cs.unc.edu> mueller@hatteras.cs.unc.edu (Carl Mueller) writes:

>Heck, I just remembered another peeve.  Why oh WHY? on the 3000 was
>there not enough memory put into the deinterlacer to support the
>Super-Hires mode?  

There are a few issues associated with that device.  First off, the memory 
consideration isn't trivial; if you have to support a field that's twice the
size of the currently supported fields, that would double an already pricey
device.  Secondly is the more technical problem of dealing with the "super
hires" display.  All of the modes that the Amber chips de-interlaces are 70ns
pixel modes -- it bypasses all of the 35ns pixel modes, which include the 
1200 x 200/400 and the 640 x 400/480/512/960/whatever "productivity" modes.
Such a conversion would be much more difficult if it was required to sample
these 35ns pixels as well as the 70ns pixels.  I don't know all the technical
issues involved, but that could significantly increase the cost of the device.

>You need a multi-sync just for this one mode.  

You really need a multi-sync for that mode anyway, a true VGA monitor may not
deal at all well with 1200 pixels in a 1200x400 noninterlaced display, since
in order to de-interlace something, you have double the horizontal rate.  So
if an interlaced 1200x400 display at 60Hz vertical referesh uses 35ns pixels,
a de-interlaced 1200x400 display would generate 17.5ns pixels.  I really don't
know what a typical VGA-only monitor would do with that.  And VGA monitors
don't necessarily support interlace, which would also rule out using the 640
x 960 interlaced display mode.

>-Carl (mueller@cs.unc.edu)


-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
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	Standing on the shoulders of giants leaves me cold	-REM