The trick is in the RF modulator. PAL Amigas carry PAL RF modulators
and NTSC, NTSC RF modulators. You can convert a PAL A600/A1200 to boot
to NTSC and vice versa with no problems, however the specific RF
modulator frequency stays the same and makes things difficult. Of
course, if you don't care about TV output(s) then it doesn't matter as
RGB out port is not affected by this, thus there are no problems with
Amiga monitors and these new funky signals which are called PAL60 and
NTSC50.