Commodore.ca: The PET, VIC, 128, 64 & More Forum

Hi,

New to this forum, and proud owner of a C64 since 1984. It has not been used since probably 1990, and I would like to revive it.
However, the power supply has been lost. I can find the pin layout online, not a problem.

The main question: The 9VAC is the reference frequency for the internal clock. Now, back then I lived in Europe (220V 50Hz), and now I live in the US (110V 60Hz). This is a European C64.
Do I have to have a 50Hz AC source for the 9V, or can I use our standard 60Hz?
Is there a jumper or something inside that will allow me to switch the unit from 50Hz to 60Hz?
I'd hate to have to build a 50Hz generator just to revive this old unit.
Thank you for your insight.

Berrie

Hi,

9VAC is used as TOD (Time Of Day / real time clock) reference for both CIA chips.
There's no hardware jumper for setting the CIA chips for 50 or 60Hz operation,
this is done through register settings.
7th bit of $DC0E (for CIA#1) and $DD0E (for CIA#2).
On PAL machines the 7th bit of both registers mentioned above are set to 1,
while on NTSC machines these are set to 0.

I'm a bit unsure whether supplying 60Hz into a PAL machine will cause side effects
other than a speedy real-time clock. But there may be KERNAL routines that are relying
on CIA timers (e.g. cycle-accurate delays), and the machine may hangs
before the poke commands can be entered.