I don't know a ton about this subject, but I do remember, back in the day, I burned what I now think was an EU copy of Soul Calibur for the Dreamcast to a disc (back in my unsavory days of youth when I did such unscrupulous things). At every startup it would display a notice asking if the game should be run in 50 Hz or 60 Hz. While this message was up, the old CRT TV image would scroll in one direction and look all weird. If I picked 50 Hz, the scrolling continued as long as the game was on; if I picked 60 Hz, the scrolling would stop and the game displayed normally.

It appears to be working. So far I haven't seen any messages and I've played and exit two-three times now. :)

The clock speed *were* sometimes different between PAL and NTSC; e.g. a NTSC NES runs at 1.79MHz, while a PAL NES runs at 1.66MHz. I don't know about the C64.

I'm not talking about the C64 though. The Mega Drive for example actually had a slower CPU. Obviously you have to slow down the video hardware, but what's the easiest way of keeping the slower video hardware in sync with the program without re-writing it? That's right, slow down the CPU, because then the program doesn't even know anything is different. I'm telling you, on some consoles they just slowed the *entire thing* down by 1/6th rather than re-write the software or anything. I'm not sure why you assumed I was talking about the C64, or why that would refute what I'd said.

EDIT: Corrected a mistake.

No, so I see. I don't know why I thought so, sorry.
Easy, that's because I'm an idiot ;-)

No worries. I didn't know that the C64's PAL version was in some ways superior though, that's kind of cool. I wonder if games that suffered from slowdown on NTSC machines ran smoother on PAL ones (albeit at a lower frame rate)?

Yeah well, it was different anyway. Since the added number of cycles per frame was a result of simply having fewer frames, it was a give-and-take situation.

But I'm guessing that for example newer C64 demos only run on PAL C64s. Since the demoscene was always biggest in Europe, I assume that's where most of the people are from, so the demos are probably made for PAL machines. And given that the point of most demos is to show how much performance you can squeeze out of the available resources, my guess is that most of them probably use every CPU cycle available for each frame.

I would imagine that most older games would run fine on either type of machine though. They probably aren't as CPU intensive. Of course, there will still be slow-down/speed-up issues when run on the "opposite" model if the movement of the sprites is linked to the frame rate.