Re: //gs 50-60Hz how ?

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <3qri9k$6vs@moose.erie.net>,
Salvatore Buttice <qsilver@moose.erie.net> wrote:
> Michael Ewen (Michael_Ewen@mindlink.bc.ca) wrote:
> :         hat if anything are the advantages to going from 50 - 60?
> 
> I assume you mean the monitor settings accessible from a 4 finger salute? 
> The only reason for that is that Europe runs on 60Hz, whereas the US (and 
> Canada I beleive) run on 50. Or I might have gotten those switched 
> around. Never was too good at electronics!

Other way around.  The US is 60 Hz, most other countries are 50 Hz.

I never saw much point in this option.  I'm in New Zealand, which has
50 Hz mains supply, but I've been running my video display at 60 Hz
since I got my first IIgs in 1987.

Since the screen is refreshed more often at 60 Hz, there is
considerably less "flicker" than at 50 Hz (I can easily see 50 Hz
refresh if I look at the screen out of the corner of my eye).

The visible screen area is also larger (50 Hz causes the border at the
bottom of the screen to get larger; this can be adjusted using the
vertical height control, but it tends to stretch the pixels).

Another point in favour of using 60 Hz: the IIgs's vertical blanking
interrupt is tied to the screen refresh rate.  If the video display is
running at 50 Hz, any VBL or heartbeat interrupt handlers will only
run 50 times a second, instead of 60.

Apple's documentation has always said that heartbeat interrupts run at
60 Hz, but this is only true if the video display is set to 60 Hz.
There are sure to be programs out there that assume heartbeat
interrupts are always at 60 Hz, and will have fixed their delays
accordingly.  This means that if these programs are run with the video
set to 50 Hz, they will take 16.7% longer to generate timeouts (e.g. a
screen blanker might take 11 minutes to blank when configured for 10
minutes).
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand