FireWire fried my motherboard!?!

[Hi-Fi Man]

This is a very odd scenario i.e. nothing to do with plugging in the wrong cables to the wrong headers.

First off my motherboard that got fried was a gigabyte EP45-UD3P. This board has an onboard TI FireWire controller that provides two FireWire 400 ports on the back of the board (a 6 pin and smaller 4 pin).

I also have a Power Mac G4 with three FireWire 400 6 pin ports provided by an onboard Lucent controller. Both machines run OS X. OS X supports networking via FireWire so I attempted to connect both computers via FireWire directly via each 6 pin port and as I plugged in the cable to the Power Mac G4, my hackintosh immediately shut off and soon after a terrible burnt smell could be smelled. The Power Mac however kept going and nothing could be smelled from it.

After some troubleshooting I verified that the motherboard was dead (won't turn on, fan spins for a second, tested different PSU). My question is has anybody heard of something like this occurring or why it could have occurred? FireWire supports hot plugging but I read that it's not recommended but I've never had issues before hand.

The motherboard in question doesn't have any noticeable burn marks but the smell is very strong around the back and back top of the board.

 

[Deders]

Sounds to me as if you had 2 conflicting electric signals, as if you were using 2 different power supplies in the same computer, unless the current is synchronised something is going to go bang.

Even if both PSU's supply exactly the same voltage, the ripple is going to fluctuate at different times so when one voltage reaches the other, they don't match and something goes bang.

In your case it could just be faulty or bad voltage regulation on the firewire circuits on the motherboard, or maybe one of the PSU's is at fault.

 

[Hi-Fi Man]

The system was only using one PSU (I just tested it with other PSUs).

 

[dave_the_nerd]

I've done exactly what you're talking about.

I think it might be a coincidence, unless there was something horrifically nonstandard about Gigabyte's Firewire implementation...

 

[Deders]

The system was only using one PSU (I just tested it with other PSUs).

Yes but each system has it's own PSU with their own independent power, once you connect these with the Firewire cable, you have 2 slightly different voltages clashing.

 

[nitromullet]

FireWire supports hot plugging but I read that it's not recommended but I've never had issues before hand.

Fairly technical document that discusses failures due to a "late Vg event".

"All 1394 PHY devices are susceptible to electrical overstress damage when exposed to a combination of high-voltage cable power and a faulty cable or connector system that allows data (TPx) and cable power (Vp) connections to engage before the cable ground (Vg) connection. This set of circumstances is known as a “late Vg” event."

They mention on page 7 that 6-pin FireWire is more susceptible than 9-pin due to the possibility of angled insertion.

http://www.ti.com/lit/an/slea072a/slea072a.pdf

This document also explains it a little on page 1 in the last paragraph.

http://www.ti.com/lit/an/slva449/slva449.pdf

 

[Hi-Fi Man]

Fairly technical document that discusses failures due to a "late Vg event".

"All 1394 PHY devices are susceptible to electrical overstress damage when exposed to a combination of high-voltage cable power and a faulty cable or connector system that allows data (TPx) and cable power (Vp) connections to engage before the cable ground (Vg) connection. This set of circumstances is known as a “late Vg” event."

They mention on page 7 that 6-pin FireWire is more susceptible than 9-pin due to the possibility of angled insertion.

http://www.ti.com/lit/an/slea072a/slea072a.pdf

This document also explains it a little on page 1 in the last paragraph.

http://www.ti.com/lit/an/slva449/slva449.pdf

Usually this late Vg event causes controller damage from what I've read, not the entire motherboard going down.