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From: wright@etsuv2.etsu.edu (BRIAN WRIGHT)
Newsgroups: comp.sys.amiga.misc
Subject: Re: fat agnus + pal + noistrackers
Message-ID: <1991Apr21.224513.46281@vaxb.acs.unt.edu>
Date: 22 Apr 91 03:35:42 GMT
Reply-To: wright%etsuvax2@ricevm1.rice.edu
Organization: East Texas State University
Lines: 25
Nntp-Posting-Host: etsuv2.etsu.edu

In article <16752@chaph.usc.edu>, wdao@girtab.usc.edu (Walter Dao) writes...
> 
>I have a NTSC machine, with 1.3 roms and have invested into a fat agnus. 
>When I switch to PAL mode (with bootmenu or fastpal), and play a demo, 
>the screen is as the programmers wanted it to be (especially in demos like 
>Rebels total triple trouble). However, the music is also slower too. 
>is it normal ? A lot of the soundtracks seem "more" right on NTSC machine.
>but slower on Pseudo Pal. 

It's called Vblank.  Because a 50hz refresh rate is slower than a 60hz
refresh rate, songs are slower in PAL.  They are timing the song off of 
the vblank timer rather than a CIA timer.  A CIA timer will play the song
the same on all machines.  Vblank timing changes to the speed of the screen 
refresh rate.  Hence, slower songs in PAL and faster in NTSC unless they use 
the CIA timer.  ProTracker 1.1b is the first tracker that I have seen that
gives you a choice between playing the song with the Vblank or the CIA timer.
Most demos, unfortunately, use the Vblank which slows the songs.  

>So how do people do if they want to write a piece of music that will be the
>same on NTSC and PAL ? is it just a Pseudo Pal quirk ? 
> 
>				Walter

Brian Wright
wright%etsuvax2@ricevm1.rice.edu