About the keyboard:
The XT keyboard returns 0xAA when it receives a reset signal.
When the MiSTer core receives the reset pulse from the CPU, it sends 0xFF to the PS/2 keyboard to receive (0xFA)0xAA.
I thought this would be useful for detecting keyboard not connected, but it actually seems to be an annoying feature.
I think changing the keyboard module to monitor the reset pulse and return 0xAA directly when it receives it would solve the problem.
Also, because 4.77 MHz is slow, there was concern that the keyboard would send the next data before the CPU could process the key code.
To avoid this, the core dropped the PS/2 clock line to Low between the time the keycode was received and the time the CPU received it.
In practice, this concern was unnecessary and only interfered with the operation of other cpu monitoring the same PS/2 bus.
About the Clock:
Gyurco is correct.
At the time I joined the MiSTer PCXT project, each module was running on a different clock that was not synchronized.
I proceeded to change several modules to run at the same clock as the chipset, with the exception of video. In doing so, due to my negligence, I created CE signals from the clocks that were in use prior to the change.
However, I think you need to pay attention to the cpu clock.
This signal is monitored on both edges by both the CPU and chipset modules.