Path: utzoo!utgpu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!sdd.hp.com!decwrl!waikato.ac.nz!canterbury!chem194
From: chem194@csc.canterbury.ac.nz (John Davis)
Newsgroups: alt.sources.amiga
Subject: Re: INFO-- Why some demos crash!
Message-ID: <1991Feb28.170806.136@csc.canterbury.ac.nz>
Date: 28 Feb 91 04:08:05 GMT
References: <1991Feb27.163953.1@happy.colorado.edu>
Organization: Chem Dept, U of Canterbury, Christchurch, New Zealand
Lines: 40

>   There's a program out called PalBoot that puts machines with the ECS into PAL
> mode-- in fact, I permanently have my screen scrunched (pot in back) to
> accomodate the higher resolution of PAL.  Unfortunately, the PalBoot program is
> rather unflexible.  Since many ST/NT songs are written for PAL and others are
> written for NTSC, I whipped up a couple of simple programs, PAL and NTSC.
> 
>    You can, too...  To put the machine in PAL mode, simply plug the value #$20
> into location $DFF1DA (LONG WORD!!!!!!).  To put it back into NTSC mode, insert
> a value of #$02 I believe (Once again, a LONGWORD!).

The trouble with just dumping $0020 or $0000 into $dff1dc is that whilst
the hardware changes over (i.e you'll get the frame rate etc changing)
the actual system copperlists don't get modified to match. This can
result in some interesting effects....
 
I've tried hacking around to get the copperlists, lib vars etc updated,
but had no real sucess (guess we'll just have to wait for wb2.0 for on
the fly ntsc/pal :-) - in the meantime the best you can do is select screen
modes at boot time - to facilitate this I knocked up a program by the
name of BootMenu (which you can find in /incoming/amiga on
abcfd20.larc.nasa.gov) which allows _user_selectable (via a menu) choice
of screen modes at every reboot (it wedges itself into the system). That
means that once you've loaded it, you can reboot at any time and re-choose
NTSC/PAL (unlike PalBoot where you've got to run it each time you want to go
PAL - a real pain).

Also it works properly with 030's etc - and it even gives you the choice
of turning of your hard-disks  to protect against 'rogue programs'.
 
Of course if you want to do it properly, wire up a toggle switch on the
appropriate line to the 1mb agnus and switch it in hardware (that way
you can _permanently_ select the screen mode of your chosing)

-----------------------------------------------------------
| o  John Davis - CHEM194@canterbury.ac.nz               o |
| o  (Depart)mental Programmer,Chemistry Department      o |
| o  University of Canterbury, Christchurch, New Zealand o | 
| o                                                      o |
| o  co-sysop AmigaINFO BBS,1200/2400 baud CCITT,        o |
| o           24 hours a day, ph NZ +3-3371-531          o |