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View Full Version : Can an IEEE 1394 cable be plugged into a USB2 header?


GTaudiophile
11-05-2005, 09:10 AM
I have this ECS 760GX-M motherboard (http://www.newegg.com/Product/Product.asp?Item=N82E16813135194) in this Antec Minuet II case (http://www.newegg.com/Product/Product.asp?Item=N82E16811129161). 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
11-05-2005, 09:13 AM
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
11-05-2005, 09:14 AM
Thanks. Just needed to be warned before I tried. Doesn't make sense that IEEE 1394 and USB cables are the same!

evilharp
11-05-2005, 09:15 AM
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
11-05-2005, 09:38 AM
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 (http://www.threewood.com/misc/cables.jpg).

GTaudiophile
11-05-2005, 07:58 PM
No additional comments on the picture I took? At the very least, teh fact these two cables are the same is confusing!

mechBgon
11-05-2005, 08:18 PM
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
11-05-2005, 08:39 PM
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 (http://www.threewood.com/misc/cables.jpg).


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.