Re: PET 50Hz vs. 60Hz screens?

From: Mike Naberezny <>
Date: Sun, 16 Dec 2012 14:25:57 -0800
Message-ID: <>
Hi Olaf,

> I presume it is possible. The reason that I think that is that the
> SuperPET ROMs provide for a 60Hz setting, and I never heard about
> separate American/European versions of that. So the 60 Hz must have been
> used on European machines as well.

I think that you're right about this, but it's possible that 50 Hz ROMs for 
6809 mode do exist and nobody has dumped them yet.  There seems to be many 
more North American SuperPETs around than European ones.

I have read that the 6809 mode has a software real time clock but I haven't 
tried to use it.  It can be accessed with the TIME$ variable in Waterloo 
microBasic.  The back of the Waterloo 6809 Assembler manual also lists date 
and time routines in the ROM.  It must not keep accurate time if the IRQ fires 
at 50 Hz but the ROMs expect it at 60 Hz.

The High Speed Graphik (HSG) board is another interesting case.  It generates 
its own video signal with a Thomson EF936x and was only sold in Europe for 50 
Hz machines.  Some people have installed it in 60 Hz machines and reported 
that it works.


Mike Naberezny (

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Received on 2012-12-16 23:00:05

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