"Navid" said:
There are 2 FET transistors on P4P800 deluxe motherboard between the AGP and
the adjacent PCI slot. They get extremely hot. Sometimes to the extent
that my CPU (P4C 2.6G) throttles down! The motherboard in that area gets
pretty hot too.
Has anybody else noticed high temperature of those transistors or is
something wrong with my motherboard?
Thanks,
Navid
There is a MOSFET next to the word "PCI 1", as pictured in
the P4P800 Deluxe manual E1323. It seems to have +5V around it,
and I don't know why Asus would need to make a switch or a
linear regulator out of a MOSFET connected to such a high
voltage.
Following over to the right, are two MOSFETs and a toriod with
a large number of turns of copper wire on it. This is a switching
regulator, making 2.5V for the DIMMs. The 2.5V copper "island"
flows back to the left on the board, and appears to be feeding the
Northbridge, and also seems to feed the second hot MOSFET you
mention. My guess is, this could be a linear regulator, dropping
from 2.5V to 1.5V for the AGP slot. That MOSFET is the one on the
right hand end of the AGP slot.
Feel both the MOSFETs and other components in the area, as the
heat could be originating from just one component, but flowing
through the general area. If both MOSFETs are hot, then either
the two MOSFETs are connected to a common circuit, and both
have been enabled at the same time, instead of just one of them.
You might be able to reduce the heat on the MOSFET next to the
AGP slot, by going into the BIOS and raising the AGP I/O voltage,
and them go to the Vdimm and drop Vdimm to 2.6V (just enough to
run PC3200 RAM). Dropping Vdimm and raising Vagp, reduces the
voltage drop across the MOSFET next to the right hand end of
the AGP slot, and since P=V*I, the power should be reduced
as well.
Unless you can get confirmation from other users of this
board, that the heat is "normal", I'd try an RMA. MOSFETs
have a safe operating zone, and the hotter they get, the higher
the resistance of the MOSFETs become. I doubt the MOSFETs
were ever intended to get that hot.
Maybe this could be caused by a defective AGP card. If you have
another compatible AGP card handy, try swapping it in and see how
hot your MOSFETs get. Since only I/O pads are supposed to be
powered by I/O voltages, the power consumption through the MOSFETs
should be in the same ballpark, for two different AGP8X video card
designs.
Paul
