Can an IEEE 1394 cable be plugged into a USB2 header?

GTaudiophile

Lifer
Oct 24, 2000
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I have this ECS 760GX-M motherboard in this Antec Minuet II case. The case has cables for the front panel: audio, IEEE 1394, and USB. The motherboard has the necessary audio headers and two USB 2.0 headers but no IEEE header. Of course the IEEE cable fits just fine onto the USB header. Can you still use the IEEE port at USB2.0 speeds?
 

Tanclearas

Senior member
May 10, 2002
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No. You'll likely fry the board, but you'll at least fry the USB header.


Edit: Posted prematurely. Damn my large hands! LOL!
 

GTaudiophile

Lifer
Oct 24, 2000
29,773
11
81
Thanks. Just needed to be warned before I tried. Doesn't make sense that IEEE 1394 and USB cables are the same!
 

evilharp

Senior member
Aug 19, 2005
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No.

The standards are not compatible, and the pin-outs are very different. You could seriously mess up anything you plug into that port (the grounds and power pins are different).
 

GTaudiophile

Lifer
Oct 24, 2000
29,773
11
81
No additional comments on the picture I took? At the very least, teh fact these two cables are the same is confusing!
 

mechBgon

Super Moderator<br>Elite Member
Oct 31, 1999
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They look different to me... one says 1394 on it, the other says USB. :) You might as well add sugar to your car's gas tank, if you're going to plug the Firewire cable into the USB header.

The wire pinout on the USB cable is undoubtedly the typical

+5V . Data- . Data+ . Ground . Ground
+5V . Data- . Data+ . Ground

And the firewire cable would be

DataA- . Ground . DataB- . +12V . Ground
DataA+ . Ground . DataB+ . +12V


So if you match 'em up, then if you plug a Firewire device into a Firewire port that's attached to a USB header, your iPod (or whatever) will get hot 5-volt power on its twisted-pair-A data lines (bad!), and grounds on one of its two twisted-pair data cables and its 12V lines. So I believe you'd probably ruin the iPod point-blank. Possibly the motherboard too.
 

evilharp

Senior member
Aug 19, 2005
426
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Originally posted by: GTaudiophile
Originally posted by: evilharp
No.

The standards are not compatible, and the pin-outs are very different. You could seriously mess up anything you plug into that port (the grounds and power pins are different).
Hmmm. They don't look different to me.

As mechbgon indicated, they are similar but they are very different.

Both use 10 pins, but the pins are assigned to different functions. Thankfully, both USB and 1394 have been standardized, so the pinouts are as follows:

USB2

1 - power
2 - power
3 - USB Dx-
4 - USB Dy-
5 - USB Dx+
6 - USB Dy+
7 - GND
8 - GND
9 - No Pin (cable usually plugged to prevent use on Firewire)
10 - NC

1394 (Firewire)

1 - TPA2+
2 - TPA2-
3 - GND
4 - GND
5 - TPB2+
6 - TPB2-
7 - No Pin (cable usually plugged to prevent use on USB)
8 - Power
9 - Power
10 - GND

The odd cable manufacturer doesn't use "blocked" connectors to save on money, which causes headaches for the end user. As you can see, the signal, power and ground pins are all different, which is to be expected as the standards are very different.
 

Polanve

Junior Member
Dec 4, 2021
2
0
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As mechbgon indicated, they are similar but they are very different.

Both use 10 pins, but the pins are assigned to different functions. Thankfully, both USB and 1394 have been standardized, so the pinouts are as follows:

USB2

1 - power
2 - power
3 - USB Dx-
4 - USB Dy-
5 - USB Dx+
6 - USB Dy+
7 - GND
8 - GND
9 - No Pin (cable usually plugged to prevent use on Firewire)
10 - NC

1394 (Firewire)

1 - TPA2+
2 - TPA2-
3 - GND
4 - GND
5 - TPB2+
6 - TPB2-
7 - No Pin (cable usually plugged to prevent use on USB)
8 - Power
9 - Power
10 - GND

The odd cable manufacturer doesn't use "blocked" connectors to save on money, which causes headaches for the end user. As you can see, the signal, power and ground pins are all different, which is to be expected as the standards are very different.
Could this damage the mobo even if you didn't plug in anything to the 1394 cable? (asking for a friend)
 

UsandThem

Elite Member
Super Moderator
May 4, 2000
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Could this damage the mobo even if you didn't plug in anything to the 1394 cable? (asking for a friend)
The user you quoted hasn't been here in 10+ years, and this thread was last active in 2005.
 
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Polanve

Junior Member
Dec 4, 2021
2
0
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The user you quoted hasn't been here in 10+ years, and this thread was last active in 2005.
lol and yet i still just plugged a 1394 cable from the case into a usb header on my new mobo and i'm wondering if i messed something up.
 
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