A solution for SATA and on board LAN going AWOL on some P5Kxx's

Hi All
Firstly a little thank you to everyone who contributes to this newsgroup
I've often found useful info, tips and solutions here. Now I hope I can help
out a little with my solution to some ASUS P5Kxx boards that do strange
things when a particular internal USB header is used. No doubt someone will
say "oh yes! we already know about that....." :-) But I've had a good look
and what I've found so far basically says, in a nut shell, "it's broken
don't use it".

So to the point, a solution for SATA and on board LAN going AWOL when you
plug in an internal USB cable in to a particular USB header :

The problem relates to a particular USB header on ASUS P5K type motherboards
that don't have the optional extra WiFi AP/extra 1Gb LAN module. It is also
possibly that the same problem may occur on other ASUS motherboards that
have a similar optional extra available.

The USB header in question is situated in the position where the optional
WiFi module would be connected. On my P5KC the offending USB header is shown
in the user guide as USB910 and is situated just below the I/O shield and
close to chas_fan2. On the motherboard it is screen printed as USB910_WFGBT
and there are 6 additional PTH's adjoining the USB header which are unused
and probably provide additional connections for the optional WFGBT module.

Now the problem is this, if you connect any USB cable or device to this
header that has anything (usually the cable shielding) connected to the pin
designated by ASUS as NC (refer to the user guide) your JMICRON SATA
controller and on board 1Gb LAN will either disappear or start to misbehave
(lots of BSOD's, intermittent boot failures and/or restarts).

The solution is to remove the wire that is connected to the NC position at
the motherboard end of the USB cable. Either cut it off close to the plug
(taking extreme care not to cut the wrong one) or if you have good eye sight
and steady hands you can remove the wire in a less destructive way by using
a very very small screw driver or a darning needle (ask your granny for one
:-)) to slightly lift the plastic retaining tab while gently pulling the
wire from the back of the plug. Once removed use some PVC tape, or plastic
heat shrink tubing if available, to insulate the end. You can now plug the
USB cable in to the offending USB header without any unwanted side effects.

The wire you have removed should be the cable shield which should be
connected to ground at the other end but does not need to be connected at
the motherboard end. This is not normally a problem if the NC pin is Not
Connected to anything as is normally the case on ASUS motherboards or if it
is connected to ground as on some other manufacturers boards. But I suspect
that ASUS on this particular occasion are using this pin along with other
unused connections associated with the WFGBT part of this header to provide
the optional extra 1Gb LAN with access to the same bus that is used by the
on board JMICRON SATA and 1Gb LAN controllers. I'm not sure exactly what
this connection is but I do know from personal experience that shorting it
to ground via the USB cable shielding makes the JMICRON SATA and on board
1Gb LAN disappear.

I would guess that even if your USB cable or device does not ground the
cable shield at the device end or perhaps badly grounds it or even connects
the NC pin in another strange non-standard way you could experience
unexpected, unpredictable and possibly intermittent problems with the
JMICRON SATA and on board LAN if it were to be plugged in to this particular
USB header.

I hope this proves useful to someone.

glyn.j.evans
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