From: barrett@iastate.edu (Marc N Barrett)
Subject: Re: A4000+DOMINO !!!
Keywords: A4000, DOMINO GFX BOARD
Organization: Iowa State University, Ames, IA
Date: Fri, 2 Oct 1992 02:37:30 GMT

In article <1992Oct1.040848.2680@sol.cs.wmich.edu> 22black@sol.cs.wmich.edu (Martin E. Black) writes:
>barrett@iastate.edu (Marc N Barrett) writes:
>
>>In article <1992Sep30.164858@cc4.kuleuven.ac.be> stud11@cc4.kuleuven.ac.be (Lode Vande Sande) writes:
>>>
>
>>>
>>>        If  I'm  correct, the performance of the AA chip set depends on the
>>>type  of ram chips you use for your CHIP ram.  Is this true ?  If so, could
>>>anyone  please  tell  me exactly what this means and with what kind of CHIP
>>>ram the A4000 comes with out the box ?
>
>>   The A4000 comes with 2M of chip RAM, which is the most that the Alice
>>chip (replacement for Agnus) can address.  I assume that Commodore is using
>>the types of RAM chips that optimize the performance of the Amiga graphics
>>system.
>
>Wrong different ram chips

   I never said the chips were the same.

>>>        The  A4000's display can range upto 1280x512 (maybe higher, I don't
>>>know), but the question is :  is this interlaced ?  
>
>>   Yes, the 1280x512 mode is interlaced.  Even worse, it is interlaced with
>>a field rate of 25Hz.  
>
>Completely wrong there.  1280x512 is de-interlaced at 30khz and the scan 
>rate is at a pal 50hz.  Nice rock steady display.

   You are completely wrong here.  All of the Super HiRes modes are "promoted"
to an autoscrolling screen with a maximum SCREEN resolution of somewhere
between 640 and 720 pixels.  None of the Super HiRes modes are "deinterlaced"
to a display with a screen resolution of 1280 pixels wide.

>>>I have read that the AA
>>>chip  set  can  produce  non-interlaced displays, but can it do this in all
>>>these  resolutions  ?  
>
>>   No.
>
>True, but only for 640x960 and 800x600.  All else de-interlace in the chip
>itself as opposed to de-interlacing outside [ as with a3000] 

   Wrong.  None of the SuperHiRes modes are deinterlaced, for instance.  The
scan doubler and promoter works functionally the same as the external 
display enhancer of the A3000, in that it only works on modes with a horizontal
frequency of 15Khz and a pixel clock of 70nS or greater.  Again, the 35nS 
Super HiRes modes are ***NOT*** deinterlaced!!

>>   The A4000 offers exactly the same non-interlaced modes as the A3000 with
>>the Display Enhancer turned on.  The Display Enhancer has effectively been
>>moved internally to the Lisa chip, but the non-interlaced modes offered are
>>exactly the same.  The highest non-interlaced resolutions offered by the 
>>A4000 are 720x480 60Hz NTSC and 720x560 50Hz PAL.  No higher non-interlaced
>>resolutions are possible.
>
>As i said all except for those modes requiring higher freq than 31khz which is 
>what i said above 62 and 50 respectively

   All except those modes requiring a frequency higher than 31Khz or a dot
clock of less than 70nS.

>>   In addition, you may have heard about an 800x600 mode, but this mode is
>>interlaced at 72Hz (field rate of 36Hz), and has a horizontal frequency of
>>24.62Khz.  It is not usable on any VGA monitors, and few multisync monitors
>>will support it.  Even if you do find a monitor that supports the rather low
>>frequency of 24.62Khz, the monitor must also support interlacing.  And even
>>if you do find a monitor that supports the 24.62Khz frequency and interlacing,
>>the display will not be nearly as sharp as a VGA 800x600 non-interlaced 
>>display.  I would ignore the 800x600 mode if I were you.
>
>First of all the C= 1960 and 1950 works fine in all modes, and could be had
>for $400.  

   That is overpriced, and I do not trust Commodore monitors.  Besides, I 
find it compeltely immoral for a company like Commodore to purposely design
a system so that only their monitors and few others can be used with the
system.  Commodore has done this with the A4000.  Hell, you cannot even use
Commodore's own 1930 VGA monitor with the A4000, for many, many, many reasons.
(For one, somebody complained on Advocacy that Amiga software will often
throw you out of a Promoted NTSC or PAL mode to a standard flickering NTSC
or PAL mode.  If you used the 1930 or just about any other monitor, your
display would be instantly reduced to garbage, forcing you to reboot the
computer to get a usable display again)

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