Re: Converting a Commodore 64 from NTSC to PAL

From: Gábor Lénárt <>
Date: Fri, 13 Apr 2012 14:56:58 +0200
Message-ID: <>
On Fri, Apr 13, 2012 at 02:48:43PM +0200, Rob Clarke wrote:
> The TOD clock on the CIA's has a control bit which indicates whether the
> clock signal is 50 or 60 hz. I could not for the life of me remember how
> this gets set by the Kernal. The CBM-II's had a jumper on one of the TPI's
> but AFAIK, the only jumper on the 64 boards was only for the clock
> divider, and not hooked up to any of the control ports. As the 64 kernal
> was region agnostic, how did it set the 50/60hz control?

Anyway, frequency of the AC input is not so exact sometimes, so TOD can be
quite un-precise. I was thinking some years ago to try to use another input
signal for the CIAs which is more stable, so TOD will be more "usable". This
can be interesting for me now, as I want to interface some SPI devices
including SD card and a real-time clock chip, but I feel more "compatible"
if softwares can use TOD, just it would be initialized from the real time
clock ...

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Received on 2012-04-13 13:00:59

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