Hum,
if i remember correctly , it`s best to stick to multiples of the bus speed; or it will slow down the data.
eg. the clock cycle (14.2Mhz?) times perfectly with 28Mhz or 42Mhz...
33 is reasonable since it`s 2½ times 14Hhz....(and within 10% of the original speed, hopefully)...
[er, or not...]