Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!gatech!udel!mmdf
From: gay%elde.epfl.ch@cunyvm.cuny.edu (David Gay)
Newsgroups: comp.sys.amiga
Subject: Re: Bug in decision for PAL or NTSC
Message-ID: <5908@louie.udel.EDU>
Date: 9 Dec 88 14:17:19 GMT
Sender: mmdf@udel.EDU
Lines: 44

In article <1329@rmi.UUCP> kkaempf@rmi.uucp (Klaus Kaempf) writes:
>In article <1994@van-bc.UUCP> lphillips@lpami.van-bc.UUCP (Larry Phillips)
> writes:
>:
>: > But what is the 'line frequency' pin from the power supply good for ??
>: > Doesn't the Amiga check that line to decide if it should display PAL (50Hz)

>: > or NTSC (60Hz) ?
>:
>: I hope not. This would prevent PAL Amigas from being used in North America,
>: and NTSC Amigas from being used in Europe.

The key phrase (I use an NTSC Amiga in Europe!).

>:[...]
>: -larry
>To clarify: PAL == 256 lines/frame, NTSC == 200 lines/frame.
>
>PAL -> 50 Hz -> 25 frames/sec -> 6400 lines/sec
>NTSC -> 60 Hz -> 30 frames/sec -> 6000 lines/sec
>
>So both need about the same dma bandwith to display a standard picture. You
>can't display 256 lines with NTSC, can you ??
>
No, therefore your NTSC Amiga in Europe (with line frequency = 50Hz) can't
display 256 lines ...
In the good (or bad ?) old days of 1.1, when the line frequency wasn't checked,

the OS would suppose that it was 60Hz when you had an NTSC Amiga, thus the
clock would be slow by a factor of 1.2. Of course, better that than trying to
display 256 lines!

>By looking at the line frequency at boot-time, the amiga should decide
>whether to display 200 lines (60 Hz, no dma-time for 256 lines) or
>256 lines (50 Hz, no 200 lines please !).
>
>Still puzzled,
>
>Klaus

Trying to muddy the waters,

David Gay
GAY@ELDE.EPFL.CH, or GAY%ELDE.EPFL.CH@CLSEP51.bitnet