Oh shit! Thanks. Good point. That actually makes it more plausible, as K is smaller.

1/2 c in circuit boards (FR-4), 1/3 c in cables, two useful numbers to remember.

Thanks, nice! But wait - so we have

1/2 c ~ 150 km/ms in circuit board.

1/3 c ~ 100 km/ms in cable. And...

2/3 c ~ 200 km/ms in fiber?

I'm a bit confused about difference between cable and fiber heh :)

Sorry, it was a typo. I meant 2/3 (including common cables and fiber optics), not 1/3.

Depends on what kind of cable? As twisted pair network cable is at 2/3.

What an embarrassing typo! I was thinking of 0.66, and somehow I thought 0.66 = 1/3 (must've been distracted by the "2" in 1/2). I should've written 0.66 or 2/3.