Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

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?

share|improve this question
up vote 3 down vote accepted

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.

share|improve this answer
Well this is really really bad, because at least with Apple machines, a fried port means a logic board replacement, and when out of warranty, you're SOL. – kch Jul 31 '09 at 3:00
Which begs the question, why aren't there self-frying cables, that would fuse before the voltage could damage the machine at the end of it. – kch Jul 31 '09 at 3:01
The powers that be make more money off of replacement machines than self-frying cables. – LawrenceC Aug 16 '12 at 19:39

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .