I am using an iMac, not a laptop but I may be able to add some information.
iMacs and Mac laptops provide 7 watts to the FW cable. I am shooting with a CF-22MS and Phocus will lose the multi-shot capability of my back. I can shoot single shots all day but I need to restart Phocus or unplug/plug the FW cable for Phocus to once again recognize my back's multi-shot capability.
I run two longish cables that work without problems when attached to a MacPro. (Mac>Lindy 5m Active Extension Cable> TetherTools 4.6m to the digital back.) The iMac's frugal delivery of only 7 watts at the FW port has me convinced I need to buy a powered FW Repeater to kick up the wattage across the cable run.
A few more watts over the FW cable should solve my problems with Phocus not recognizing multi-shot capability after 5-10 minutes of idle time. (BTW, I have FW ports because all my Macs are 2010s so I can still run Rosetta.).