I've been noticing in some ATX PSU, they have been putting ferrite rings (that's the round thing I see on the end of video cables right?) claiming that it reduces EMI and improves quality of the video output as well as system stability.
My intuition says that's bullshit because on those leads, the PSU is delivering power at 12V level, unlikely to be affected significantly by EMI. Then there are all those caps on the cards and motherboards that would probably deal with any ripple/noise etc already.
But of course not having any formal training in EE means I could be the one getting it all wrong. So the question to all the experts is that: Are these on an ATX PSU leads there for a real engineering purpose or just marketing as I believe?
TIA!