Everyone's used T&M equipment that has no clock sync capability, or that has fixed unidirectional 10 MHz in/out ports.

What other clocking schemes are out there? (Thinking mostly oscilloscopes but also interested in specans, signal generators, AWGs, etc). What other refclk frequencies are common? Do devices have single bidirectional clock in-or-out-but-not-both-at-once ports? Etc etc

For background: we're looking to overhaul the clocking APIs in libscopehal and want a better survey of what types of clocking schemes are out there so we can account for all of them