Here’s a histogram of one track off an amiga floppy disk. Notice the peaks near 4us, 6us, and 8us.
I’ve got this data from my logic analyzer, crunched through my little C proggie, and then graphed with Excel.
This shows roughly 45,000 delta Ts, the time between each transition. The first group, of course, the ’10′s, second ’100′s and the third, ’1000′s.