Newsgroups: comp.sys.mac.misc
Path: utzoo!utgpu!watserv1!watcgl!imax!dave
From: dave@imax.com (Dave Martindale)
Subject: Re: Surely A Iifx Blows An Amiga 3
Message-ID: <1990Nov5.034615.7403@imax.com>
Organization: Imax Systems Corporation, Oakville Canada
References: <1990Oct23.193646.8067@usenet.ins.cwru.edu> <1990Oct30.171538.14327@imax.com> <8350@darkstar.ucsc.edu>
Date: Mon, 5 Nov 90 03:46:15 GMT

In article <8350@darkstar.ucsc.edu> davids@ucscf.UCSC.EDU (Dave Schreiber) writes:
>
>In article <1990Oct30.171538.14327@imax.com> dave@imax.com (Dave Martindale) writes:
>
>[...]
>
>>It is not possible to provide "workstation" quality in screen images
>>while using NTSC-standard (actually EIA RS-170A) video timing.  Amiga chose
>>to use RS-170 timing, and so it fits in the low-cost video world very well.
>>The Mac family chose to be a workstation, with video suitable for that world.
>
>Wait a minute, I think you changed definitions of 'video' between the third
>and fourth line :-).  If your goal is to produce NTSC output, then you need
>interlacing.  There's no such thing as "low-cost" video vs. "workstation"
>video (at least in the area of timing, which is what you seem to be
>implying).  I agree that the Mac is currently better at such things as
>1024x768 w/16M colors, but that's not video.

Not at all.  As I use it, "video" is any signal or set of signals used to
drive a raster-scan display device.  This includes NTSC/RS-170, but also
includes HDTV (all variations), plus all of the unique formats put out
by Sun workstations, SGI workstations, VGA boards, and everything else.

I could have said "low-cost NTSC video" in the third line, but I thought
that was obvious.  When I talk about the Mac as a "workstation", I mean
that its video frequencies and bandwidth are at least up in the lower range
of that used by computers sold as workstations.

The thing that most obviously distinguishes NTSC-compatible video from
what I refer to "workstation" video is the horizontal sweep rate.  Current
workstations mostly use a H frequency of about 50-70 kHz, and even hardware
built many years ago was using 30 kHz, while NTSC is 15.7 kHz.  Video bandwidth
for NTSC is about 4 MHz, while workstations need 25-100 MHz.  All that extra
bandwidth goes towards displaying more pixels and eliminating flicker by
refreshing the whole display faster.

>You're assuming that the FlickerFixer affects the entire machine.  Actually,
>the FlickerFixer works as a separate entity.  A 15.75Khz video signal
>comes in, and a 31.5Khz (scan-doubled or de-interlaced) signal comes
>out through a separate port.  In theory, you can hook up your multisync
>monitor to the FlickerFixer and your genlock to the regular Amiga video
>port and have the best of both worlds.

Ok, so the FlickerFixer is a separate frame buffer that doesn't affect
the NTSC output.  So you have two frame buffers that show the same
image, and which are limited to a 30 Hz update rate.  Does the
FlickerFixer plug into the Amiga, or is it a separate outboard box?  It
still seems rather silly to have a whole second framebuffer's worth of
video memory and not be able to display a second image.  (It makes
about as much sense as buying a second microprocessor called a "print
buffer" because your operating sytem can't multitask.)

Anyway, if you're willing to pay for a second framebuffer, you can have
non-interlaced video on an Amiga.  By the same token, buying a second
framebuffer can give you genlock NTSC capability on the Mac.  (Or a second
high-res screen - the Mac is more flexible that way).  That's somewhat
beside the point.

Most users use the standard video.  The Amiga's standard video is well-suited
to "desk top video", and the applications available for it reflect that.
The Mac's video is unusable for DTV, but fine for "desk top publishing",
and that's why there is so much DTP software for the Mac.

	Dave Martindale