Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!mcvax!cernvax!ethz!visinfo
From: visinfo@ethz.UUCP (VISINFO Moderators)
Newsgroups: comp.sys.amiga
Subject: Re: 60 Hz on PAL (50 Hz) Amigas
Keywords: 50Hz 60Hz NTSC PAL
Message-ID: <1508@ethz.UUCP>
Date: 6 Jul 89 11:53:18 GMT
References: <3303@shlump.dec.com> <1494@ethz.UUCP>
Reply-To: visinfo@bernina.ethz.ch.UUCP (VISINFO Moderators)
Organization: ETH Zuerich, Switzerland
Lines: 57

Discussion: 60Hz on PAL Amigas
******************************

A number of people have asked questions about the 60Hz emulation. Here are
the answers to some of the most interesting questions:

Question 1:
If 60Hz can be done, and the range is not limited, so shouldn't let's say
70Hz also be possible?

Answer:
Yes, 70Hz is possible, by principle. However there is not a very large
advantage in it, because
   1) you have a further loss of vertical resolution,
   2) software would not support this and 
   3) I'm not sure if Amiga monitors in USA can cope with that frequency
      (in Europe, the 1081/1084 stop at 64Hz).


Question 2:
If the Amiga can be made send it's dispaly output at any VB frequency,
so why don't we get a "PAL 50Hz emulator", too?

Answer:
OK. Why not. My only problem is that I do not have an NTSC/60Hz system,
which makes it difficult for me to develop and test such a thing.
Also, I'm afraid some problems could come up that aren't there in the
other "direction". Namely: Maybe Sprites don't appear exactly the right
way in the extra portion of the screen. But let's not give up hope yet.
I still have an old NTSC Agnus for my AMIGA1000 somewhere. Because many
people showed interest in a PAL/50Hz emulation, I'm going to unscrew the
old lady to be able to check that out.


Question 3:
Can we get more resolution by setting the VB rate below 50Hz?

Answer:
No, not really. Basically yes, but it's almost impossible to make it work
correctly with AmigaDOS (I'm not a specialist when it comes to graphics-
library and intuition hacking, so maybe I'm wrong to say this.)
You could make a low-level programmed application which runs in 45Hz mode
and then has a usable area of about 300 noninterlaced lines in the vertical
direction.
However, the same problem as explained in answer #2 could appear:
Bitplanes work fine, but sprites get confused in the extra portion of the
screen. Also, this kind of display is not likely to work with most
common monitors, not even multisync type ones.

F. BURGEL


/* -------------------------- SG (Simeon Graphics) ---------------------- */
/* Peter Simeon             |       //                             //     */
/* UUCP: ...visinfo@bernina |      //    Long live the AMIGA!     //      */
/* BIX:  hardwiz            |    \X/                            \X/       */
/* ---------------------------------------------------------------------- */