Don said:
On an ASUS P4P800S motherboard (2004) the four back-
panel USB jacks now seem unreliable (intermittent.) The two
front panel USB jacks appear OK.
1. Is this a known problem with Asus MBs? (Perhaps few
people still run a year 2004 mb.)
2. Is my simplest solution simply to add a PCI card with
multiple USB jacks?
Chipset is 848P/ICH5.
This is a picture of an ICH5. The ICH5 has a problem with
USB ports. Static into a USB port, can cause latchup failure.
Latchup failure, is a phantom PNPN junction (SCR) path from
+5V to GND, through the affected part. The burn mark, is right
over top of the pins that connect to USB. The PNPN junction won't
release, until all power is removed from the computer, and
affected users can never turn it off fast enough (since
the burning smell is your first clue).
http://onfinite.com/libraries/179057/2ea.jpg
There are two failure cases noted. Either the chip
burns and the board won't boot any more (major failure,
as pictured above). Or, all the USB ports pop at the same time,
and won't respond (minor failure). In that case, the bond
wires inside ICH5 pop, before the chip is physically burned.
The logic blocks still work, you can still see all your
(chipset based) USB entries. But at the physical levels,
none of the USB ports are electrically connected to the chip
innards, preventing USB devices from being detected.
Intermittent, is something new. I haven't heard of that one.
A PCI USB2 card would be the cheapest solution. If that
doesn't work, then it's some kind of driver or software
issue.
Another thing you can check, is your USBPWxx jumper blocks.
Wiggle the jumper plug a little bit, on each one. Your
USB problem could be a bus powering issue, where the jumper
plug is oxidized and making poor contact. See if things
improve, after you wiggle each one. That jumper plug, allows
you to choose whether the USB ports are powered by +5V
(strong) or +5VSB (weak). The +5VSB choice, is for when you
want a USB port to be able to wake the computer. If you
don't need waking capability, then select +5V with the jumper.
Your board has a total of five jumpers of that type:
KBPWR1
USBPW12
USBPW34
USBPW56
USBPW78
Modern motherboards no longer offer the jumper block.
Instead, the choice is fixed to +5VSB. That saves the
pennies of cost, for gold plated pins on the jumper block.
HTH,
Paul
