Can a FireWire cable fry one or both machines' FW port that it connects to?

Question

I always lug around a firewire 400 cable with me and my white MacBook.

Recently I connected my MacBook with said cable to a 1.5yr old MacBook Pro, and that machine's port died, and later on the entire logic board started going berserk. I assumed the faulty logic board was the problem to begin with.

Today I connected the MacBook to a white intel iMac 17", and now both the iMac's and my MacBook's firewire ports are dead.

Here's what is consistent throughout all borked machines:

• Target disk mode boots, but disk does not appear on a good machine with a good cable
• Connected peripherals don't work, disks do not show up on disk utility
• In system profiler, all information that is shown is "FireWire Bus: Maximum Speed: 400…"
• On occasion, it'll also show, in red, "Unable to list FireWire devices."

This is all the trouble I've ever had with FireWire, and the only things in common to all situations is the cable I used, and the white MacBook. Since the MacBook came away unscathed from the first situation, and FireWire worked fine on it up to today, I'm inclined to blame the cable.

So, can a FireWire cable fry the port(s) that it connects to?

Answer 1

It is obviously possible to plug the wrong thing into a cable and fry whatever is on the other end. It seems like an unlikely scenario to me, but since according to Wikipedia, firewire is rated to "supply up to 45 watts of power per port at up to 30 volts". So if the wire were to have an internal short it could conceivably send the power down the wrong pin and cause problems.

Since the MacBook pro was on the cable at both events it is likely the problem. It may have been having issues (sending too much voltage down the wrong pins). It fried the first, then the second and then finally gave out itself. I actually had a similar situation recently on a laptop with the USB circuit that took out a few devices before giving up the ghost itself a week later.