There are several references mentioning 1/3

http://www.controllersandpcs.de/lehr...k/edskap05.pdf

http://www.ece.cmu.edu/~ece740/f11/l...-datasheet.pdf

Second reference states "asymmetric" as you mentioned already. And 33% duty cycle (Page 4). Question is now: 1/3 or 2/3 ?!

My cpu line was U880 (Z80), 6502 and then 386 by AMD, so I have no experience with 8086...