home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Amiga Format 39
/
af039b.adf
/
mode_switch.txt
/
mode_switch.txt
Wrap
Text File
|
1992-08-14
|
9KB
|
199 lines
DISPLAY FREQUENCY SWITCHER
~~~~~~~~~~~~~~~~~~~~~~~~~~
This is a simple utility that allows the video display frequency to be
switched between 50 and 60 Hz. To be able to use the switcher your Amiga
must be equipped with the ECS Fatter Agnus chip (Model 8372A) or better.
To run the programme from the Workbench simply double click on the
'Mode_switch' icon. To execute from the CLI, enter the command
'MODE_SWITCH'.
When the programme starts it will detect whether the machine is currently
operating in 50 or 60 Hz and will switch to the opposite frequency.
A window will open to inform you of this. Press the left mouse button
anywhere on the screen to close the window.
The switcher will now become resident in memory, this will allow you to
switch between the two frequencies at any time that Exec is executing.
To switch to 50Hz (PAL) use the keys Ctrl + Alt + F1, for 60Hz (NTSC) use
Ctrl + Alt + F2. The keys Ctrl + Alt + F3 will remove the resident part of
the switcher but will leave the display in the current frequency.
If you reboot the machine (Ctrl + L-Amiga + R-Amiga) while the switcher is
still resident, it will re-install itself, the screen will flash when this
happens.
During the reboot process, holding the left mouse button will switch to the
non-default frequency, and configure the operating system to use that
frequency, but will not re-install the switcher. Holding the right mouse
button during reboot will switch frequencies, but will not configure the
system. Holding both mouse buttons during reboot will totally disable the
switcher and return to the default frequency.
KICKSTART 2
~~~~~~~~~~~
Kickstart 2 machines appear to have some quirks that can cause visual
problems with display switchers and certain other software, these problems
and some solutions are listed below:
Display frequency resets to default on reboot:
When kickstart activates the display, either for the kickstart prompt, or
when DOS begins to boot, the display resets to the default frequency, even
when the switcher is installed. This has prevented certain display switchers
from functioning (Hacktrick.60Hz, Amiga Format coverdisk 23, and possibly
others). When this happens simply use the Ctrl + Alt + F1/F2 keys to select
the required frequency.
Display frequency resets to default on execution of some DOS packages
(Deluxe Paint III, OctaMED, possibly more):
When OctaMED executes (yes I do know it has a nasty habit of locking up on
Kickstart 2), the display is switched to the default frequency, this may
also occur with some other packages. When this happens use the above
solution.
Deluxe Paint III works slightly differently, and does not require a switcher
in order to change the display frequency. When Deluxe Paint III executes,
it tries to use the mode you specified on the selection screen. This will
always go into the default mode unless the correct monitor type has been
setup on the Workbench disk. For example, to use NTSC mode on a PAL
machine, drag the NTSC monitor from MonitorStore (on the Extras disk) into
Monitors (on the Workbench disk, it needs to write to the disk, so use a
copy of Workbench) and reboot the machine back to Workbench. Now when you
select an NTSC mode, Deluxe paint switches into 60Hz for you, and if you
change mode back to PAL, it will switch back into 50Hz. If you wish you can
setup workbench to use the other monitor as default by using ScreenMode in
the Prefs drawer (interlace is almost bearable on 60Hz).
The Kickstart boot menu is activated when holding both mouse buttons on
reboot:
If both mouse buttons are held down when Kickstart activates, a boot drive
selection menu is displayed, this does not interfere with the switcher
(It is deactivated and the display resets, as is should) but it is
inconvenient (Especially if you don't know how to use it (Does anybody?)).
If the boot menu is displayed, simply click on the drive that you wish to
boot from. To prevent the menu appearing simply release the mouse buttons
as soon as the display stops flashing.
PROBLEM SOFTWARE
~~~~~~~~~~~~~~~~
There are also some problems that can arise on any machine, these are listed
below:
Some software works but audio/visuals are incorrect:
Some software will work with the switcher, but may not seem or look correct
for various reasons. Games seem to be the only problem titles, but there
could always be serious packages which suffer from similar problems.
Xenon 2 - Music is way out of sync.
On quite a lot of games the music runs faster, but this is a fine example of
what can happen if you have speech in the music. When Xenon 2 is playing
the music, it starts a sound playing perfectly, but as the timing routine
is running faster and the sounds are played at the correct frequency, it
sometimes (well most of the time really) cuts the sound short so you get
'interesting' results, things like shortened speech (shorten spee!). Not
very good to listen too but it can only be fixed by using 50Hz mode.
Cosmic Pirate and Rainbow Islands - Run out of processor time in
60Hz.
Unfortunately this can only be fixed by using 50Hz mode, see notes.
Some software refuses to load or simply crashes:
There is some software that refuses to work when the switcher is active, the
only known titles at the moment are games, but there may be other types.
There are several different solutions but these are not obvious and will
rely on experimentation, the problem titles that we have found and the
solutions are as follows:
Arkanoid II (Revenge of Doh) and Silkworm - Crash on loading.
Hold the right mouse button down during reboot.
Night Shift (MAX Compilation) - Refuses to load.
Refuses to load while the switcher is active in memory, trying to disable
the switcher from the CLI results in a system crash. On a non Kickstart 2
machine holding the left or right mouse buttons during reboot may work.
Armour-Geddon, Lemmings and Mega lo Mania - Crash or hang.
Refuse to load, there does not seem to be any way to use these titles in
60Hz mode. Mega lo Mania crashes after the title sequence.
The switcher fails to re-install itself after a reboot:
Most games software and some other software do not allocate memory in an
Exec friendly manner. These can overwrite the resident part of the switcher
preventing it re-installing after a reboot.
Software tested and found to work without problems includes the following:
AMOS 1.3, Backlash, Blood Money, Castle master, Devpac 2, Drakkhen, Flood,
FOFT, Microprose Grand Prix, L.E.D. Storm, Populous, Populous II, R - Type,
Shadow of the Beast, Speedball (Modifies display when 60Hz detected),
Stunt car Racer, Super Off Road, Turrican (Power Up compilation), X - Out.
NOTES
~~~~~
Contrary to popular belief, switching the display frequency does not affect
the processor speed of a machine, it only affects the screen redraw and
Copper frequencies, since most software uses these as update timers it
gives the illusion that the machine is running at a different speed, but in
reality it is only that the software is getting a different amount of delay
time. Normally this does not matter, since most software waits for the next
display cycle after updating the screen before displaying it, but some
software decides to display the screen every so-many display cycles. When
running NTSC software on PAL frequency, there should be no effects other
than the software running at a different speed (Usually slower but may be
faster depending on the normal amount of free processor time). But running
PAL software at NTSC frequency, if poorly written can cause the screen to
be displayed before it is completed, this causes horrible glitching, and can
also cause the processor to become overworked, when this happens everything
slows down to let the poor 68xxx catch its breath.
The switcher has been tested on a Kickstart 2 - A1500 with 1 Mb chip, 2 Mb
fast RAM and a GVP 52 Mb hard drive, and also on a Kickstart 1.2 - A500
with 1/2 Mb chip and 1/2 Mb fast RAM (which is not capable of frequency
switching but most software can't tell the difference), both of which are
PAL machines, we have not been able to test using a true NTSC machine.
ADDITIONAL FEATURES
~~~~~~~~~~~~~~~~~~~
Another problem when running some games on a Kickstart 2 machine that has
nothing to do with the switcher, is that the blitter masking bits are
sometimes set incorrectly, this can cause the edges of graphic blocks and
polygons, to appear corrupted.
When the switcher re-installs after a reboot, the blitter mask is cleared,
to make use of this feature, you must have the game disk inserted when you
reboot, otherwise the mask will be reset.
The only titles we have found so far to suffer from this problem are Cosmic
pirate and FOFT.
CREDITS
~~~~~~~
The switcher was developed and written by P. Sharpe,
documentation by C. Sharpe.
Programme code (C) Copyright 1992 P. Sharpe.
This utility may be freely distributed under the following conditions:
This documentation must always accompany the programme.
The programme code or documentation is not modified in any way.