20.000.000 is divideble by 2... so it doesn't create "blindsteps"...
mmh... don't know... maybe in future I would understand it in detail...
maybe my knowledge is much too low, to get it in my brain...
or my brain is much to small for this mathematics 
doesn't matter... i will simply try it.... UsbAspLoader is supporting USB at 20 Mhz while insert Blinsteps in mcuinstructioncode to simulate 16Mhz.
Crazy...
Advantage is, that i can use lowspeed USB and 20Mhz... an you teached me that a little bit errors in communication are aceptable.
PWM and so on, i will test it, if it mets "my doing" in precision.
I think so.
I think thats a very easy and lowcost, aceptable middleway for simple playing and first steps....
If thats crap, i will change my quarz to 16Mhz... that should be no problem.
Greetings ChrisS