how to set a maximal speed of Agon ...

[JanB-ctrl]

have a silly question: when the eZ80 and VDP have only loose connection (using serial port), then each ca work on own clock frequency. So can the eZ80 be switched to chips max frequency (like a 20MHz, ... etc)?
I mean something like a speed tunning .... ;-)
(if the used frequency is dictated by communication protocol, then the next question is: can we we communicate and work on a different frequencies?)