By default, the Hardware Manager 'Auto connect' option to connect to hardware uses the fastest cable frequency.
How can I change it to a slower speed?
If the slower cable frequency needs to be set, you can start the hw_server with a slower frequency using the following option before launching the Hardware Manager.
For instance, the following will set the default cable frequency to 1Mhz:
hw_server -e "set jtag-default-frequency 1000000"