Using A1200 NTSC with Pal

[Jose]

I know this has probably been asked already but...
What are the differences between PAL and NSTC versions, just the output screen on bootup? I seem to remember system clock was different too... but there was some jumpers on A4000's to choose PAL or NTSC so I'm confused... I think the system clock is predifined for each version but the difference is minimal, so you could turn one into the other in A4000s is this correct?
What about on the A1200? Can you turn an NTSC A1200 into a PAL one?

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[Jose]

I forgot the obvious question also, will there be noticeable differences between an NTSC version with a PAL TV and a real PAL one? I remember consoles had problems...