I forgot to mention that "PAL/NTSC mode xx.yy blahblah" log line frequency values are mostly informal only.
Values may not be always correct in some situations, calculating correct value in advance isn't that simple, biggest problem being interlace because it is impossible to be sure if current field is interlaced without also checking following field (single field interlace does not exist) which currently means "external" vertical frequency does not correctly change when interlace switches on/off. (~0.16% difference or so, 2*312 vs 625 scanlines or 2 * 313 vs 625 scanlines)
Interlace bit may be modified anytime. Also actually generating interlaced frames does not always match state of interlace bit.
Amiga programs see correct timing but non-vsync mode "real" world timing is still the exact same 49.xx/50.xxHz (VSync of course can't ever change because there is only single 50Hz PC rate)
Confusing, isn't it? Emulated hardware timing is always correct but what you actually see may not be exactly same! Think it as a some kind of time warp between your monitor and emulated universe
(I'll probably move this thread to another thread soon)