From: barrett@iastate.edu (Marc N Barrett)
Subject: Re: Unix for the masses, was Re: C= (Sweden) does things right!
Organization: Iowa State University, Ames, IA
Date: Tue, 15 Sep 1992 01:59:31 GMT

In article <1992Sep14.194743.5865@news.uit.no> terjem@stud.cs.uit.no (Terje Normann Marthinussen) writes:
>mIn article <1992Sep14.182904.20822@news.iastate.edu>, barrett@iastate.edu (Marc N Barrett) writes:
>>In article <1992Sep13.210310.15279@ultb.isc.rit.edu> eas3714@ultb.isc.rit.edu (E.A. Story ) writes:
>>>>   Now if Commodore had designed into the AA chipset some high-resolution
>>>>non-interlaced display modes on the order of 1280x1024 or higher with limited
>>>>color capabilities, Commodore could have been able to push into the low-end
>>>>UNIX market with Amiga UNIX systems that are dirt cheap to manufacture and
>>>>yet good enough to actually be sellable as UNIX workstations.  But with the
>>>>AA chipset having no non-interlaced Productivity-style modes with resolutions
>>>>higher than 640x480, they will not be able to do this.  
>>>
>>>Huh?  C= specifically mentions the same altering of resolution
>>>capability as in the ECS in their "A4000" press release!  The AGA can do
>>>1280 across, dude.  There's nothing preventing the AGA from doing
>>>800x600 in 16 colors, 1024x768 in 4 colors or 1280x1024 monochrome all
>>>noninterlaced.
>>
>>   sorry, but you cannt get solid technical details from press releases.  First
>>of all, the AGA Lisa chip cannot generate any resolution modes that are not
>>also possible (but with more limited color capabilities) in the ECS Denise.
>>If you cannot generate a certain resolution mode with the ECS Denise, then it
>>is not possible with the AGA Lisa chip either.
>>
>>   The Lisa chip does include an on-chip scan-doubler/deinterlacer, but this
>>is really only slightly improved from the external display enhancer of the
>>A3000.  It now handles all 15Khz modes, including SuperHiRes.  But it is
>>still not capable of deinterlacing any modes that are not 15Khz PAL/NTSC modes.
>>This means that the Super72 800x600 mode is always interlaced in the AGA
>>chipset (it's 24.62Khz), as is the 640x960 Productivity Interlaced mode (which
>>is 31Khz).
>
>What is the point of scan-doubling it when it is already 31Khz?
>Oh, and what monitor is capable of a 62Khz refresh rate?
>Shouldn't it already be flicker free at 31Khz?

   Ask any Amiga 3000 owner if the Productivity Interlaced mode flickers on
their system.  All of them will say 'yes' (well, all of them that can see).
The Productivity Interlaced mode is both 31Khz and interlaced, and it 
flickers.

>What I'm a bit curious about though is the 24.62 Khz refresh rate... 
>Is this good enough for a flicker free display??

   Flicker is totally independent of the horizontal frequency of the mode.
Flicker is dependent on the vertical frequency of the mode.  For Productivity
interlaced, the horizontal frequency is 31Khz, but the vertical frequency
is 30Hz, so it flickers.  For Super72 on any Amiga (including the A4000),
the horizontal frwequency is 24.62Khz, but the vertical frequency is 36Hz,
so it also flickers.  The flicker is slightly less than for the normal NTSC
mode, but still very noticable.

>I just can't remember having seen this refresh rate earlier, so could anybody
>tell me if it's supported by most of the monitors out there?

   Not all that many will support it.  Most mulitsyncs will not support it,
as most can only handle frequencies of 31Khz and higher.  Commodore's 
monitors and the occasional off-brand wide-band multisync are the only ones
that will handle it.  VGA monitors will not handle it.  (My monitor supports
it, which is why I can give you first-hand accounts about how bad the
flicker is in this mode)

>Terje Marthinussen
>terjem@stud.cs.uit.no

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| Marc Barrett -MB-  |  email: barrett@iastate.edu
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