P4P800 deluxe usb/firewire connector issue?

  • Thread starter Thread starter Peter B.
  • Start date Start date
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Peter B.

Upon my recommendation, one of my friends bought a new P4P800 deluxe
motherboard to upgrade his system. Last night he called me to tell me
that the front USB connectors did not work.

When I took a look at his machine this morning, he had connected the
Firewire cable to the USB connector. I switched the cables around and
the front USB ports now works fine.

His concern afterwards is that the P4P800 deluxe manual says that
connecting a firewire cable to the motherboards usb connectors will
damage the motherboard.

Am I correct in presuming that because the firewire cable that had
been mistakenly connected to the usb connector on the motherboard
never had a device connected to it is the reason the motherboard was
not damaged?

I'm guess that if he had plugged a firewire device into it that it
would have shorted out because usb and firewire use a different
pin-layout.

Pete
 
I believe the potential problem is that the internal firewire cable
shorts certain pins together because they are common (both ground or
both power). The internal USB cable does the same thing.

Unfortunately, pins that are OK to short together on one header
aren't OK to short together on the other header. For example,
what are common ground pins on one, are differential signals on
the other. It is possible, that by shorting differential signals
together, you can burn out the drivers on the motherboard,
especially because if one is "high", the other is always "low".
 
I wonder why attaching the firewire cable to the USP connector on the
motherboard did no damage. Everything is working fine, including the
USB front ports?

It would be a real advantage if USB and Firewire cables used
different connectors or at least if the computer case manufacturers
would label them.

Pete
 
Peter said:
I wonder why attaching the firewire cable to the USP connector on the
motherboard did no damage. Everything is working fine, including the
USB front ports?

It would be a real advantage if USB and Firewire cables used
different connectors or at least if the computer case manufacturers
would label them.

Pete
Click to expand...

Generally, if nothing had been connected to the improprly
setup front panel USB port or had bridged any of the circuits,
then everything is fine. Take a look at the schematics of the
pinouts that were connected and check if any electrical
potential had occurred. If none, then all is fine. And,
if one is so careless or unknowing as to attempt a hookup,
it is also not your fault if any problems occur.
 
From what I can discern from the pin out, it appears that the two
left pins (starting with pin 1) are +5v and -5v on the usb connector
on the motherboard. The same pins on the Firewire connector are
labeled TPAO+ and TPAO-.

I am just guessing that they are data pins? It does not appear that
the two 5v pins on the usb motherboard connector were either shorted
together or to ground when the Firewire cable was connected to the usb
connection.

I use a usb hub connected to the back of my computer and I didn't
connect either the USB ports on the front panel. Since I don't have a
Firewire device, I didn't connect it either.

I guess that my friend got a pass on this one. I just wish that they
would use different connectors for USB and Firewire. At least, it
would be a great idea for the case builders to label them.

He bought the same Antec case that I have and neither of them labeled
the USB or Firewire cables. I guess that if I had connected them on my
machine that I would have had the presence of mind to warn him of this
problem.

Anyhow, his machine is purring along. I guess that it survived the
mistake without injury?

Thanks - Pete
 
Since there is no real standard for motherboard connections, I don't
know why the pinout used by ASUS for the USB header and the pinout
used by ASUS for the Firewire header aren't the same.

Both are 5x2 headers with the same pin removed for "keying". Both
require two power pins, two ground pins, and two sets of differential
signals. I can't see even one reason why they could not match up. This
way, simply miss-connecting the wrong internal cable could never,
ever, by itself cause damage.

I guess I just value consistency and fault tolerant designs more than
ASUS. :(
 
The pinout diagrams that ASUS provides with the motherboard show that
both the USB and Firewire connectors on the MB do use a 5x2 header
with on pin missing. But what these pins do in the two configurations
- firewire and USB - are very different.

That is what can make connecting the firewire and USB cables
confusing. They both have the same layout.

Pete
 
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