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?)

[stevesims]

the two chips do work at different frequencies, yes

the eZ80's comms speed is directly tied to its clock speed. this means that if you made the eZ80 run faster you'd need to make custom changes to MOS to ensure that the comms speed stayed the same. there are restrictions on how the comms speed is derived, so that would restrict the clock speeds you could use.

I don't think the same is entirely true with the VDP/ESP32, but I'm not aware of a way to persuade an ESP32 to run faster than 240MHz.

we're driving the UART on the ESP32 about as fast as it can go - in principle it can go higher, but from what I'm seeing most people struggle to get it to go much beyond 500kbit, and we're managing to get it to work at 1mbit so we seem to be winning there already