I just only want to send note to myself. Z80 CPU clock must be 5Vpp and pure TTL levels sometimes are to low for good and stable CPU work.
Even this old CPU is very stable at 5Vpp clock, meanwhile 3.3Vpp was too low. Some CPU versions are working fine, but some are very unstable. 3V CPLD output was good only for CMOS version, meanwhile NMOS was not working- only 2..3 CPU cycles.
This information is not written in all available datasheets.