Strange Power Supply Issue

  • Thread starter Thread starter Todd Martin
  • Start date Start date
T

Todd Martin

I have a 500W power supply that has run stably with a 2.8GHz Pentium 4
CPU on a ASUS P4C800 Deluxe mobo over the past 6 months. The other day
I was given a 3GHz Pentium 4 CPU. I swapped out the old CPU and fan
and installed the brand new boxed CPU and fan. However ever since I
have made the swap over, the fan in the power supply has been working
about twice as hard as it did when the 2.8GHz cpu was installed. It is
now twice as loud as it was before and the extra noise is quite
annoying.

Has anyone else ever experienced this problem? What could possibly
make the fan of a power supply work harder like that. Surely the extra
power to run a measly 0.2GHz of extra CPU clock speed in a CPU is not
enough to cause this effect in a 500W power supply?

Another annoying new feature since the CPU swapover is random power
supply shutdowns. Sometimes when I am making the system work hard,
the system suddenly does down. It is like someone has come along and
pulled the plug out of the wall socket. I am suspicious that perhaps
the new heatsink and fan assembly is not making proper contact with
the top of the CPU resulting in inefficient heat transfer, and an
overheating CPU.

I checked with the ASUS website and noticed some circuitry that
appears in several of their boards called ASUS C.O.P (CPU Overheating
Protection). However this technology is not listed as being part of
the ASUS P4C800 Deluxe. Can anyone confirm if it is actually there or
not?

I shall take the cover off the case tomorrow when I am not so tired
and make sure I haven't done something bonehead like connecting the
CPU fan power supply to the case fan supply by mistake.

I was always under the impression that power supply fans were not
variable speed.
 
Todd Martin said:
I have a 500W power supply that has run stably with a 2.8GHz Pentium 4
CPU on a ASUS P4C800 Deluxe mobo over the past 6 months. The other day
I was given a 3GHz Pentium 4 CPU. I swapped out the old CPU and fan
and installed the brand new boxed CPU and fan. However ever since I
have made the swap over, the fan in the power supply has been working
about twice as hard as it did when the 2.8GHz cpu was installed. It is
now twice as loud as it was before and the extra noise is quite
annoying.

Has anyone else ever experienced this problem? What could possibly
make the fan of a power supply work harder like that. Surely the extra
power to run a measly 0.2GHz of extra CPU clock speed in a CPU is not
enough to cause this effect in a 500W power supply?

Another annoying new feature since the CPU swapover is random power
supply shutdowns. Sometimes when I am making the system work hard,
the system suddenly does down. It is like someone has come along and
pulled the plug out of the wall socket. I am suspicious that perhaps
the new heatsink and fan assembly is not making proper contact with
the top of the CPU resulting in inefficient heat transfer, and an
overheating CPU.

I checked with the ASUS website and noticed some circuitry that
appears in several of their boards called ASUS C.O.P (CPU Overheating
Protection). However this technology is not listed as being part of
the ASUS P4C800 Deluxe. Can anyone confirm if it is actually there or
not?

I shall take the cover off the case tomorrow when I am not so tired
and make sure I haven't done something bonehead like connecting the
CPU fan power supply to the case fan supply by mistake.

I was always under the impression that power supply fans were not
variable speed.
Click to expand...

Northwood 2.8GHz/FSB800 (0.13u 512KB cache) 69.7 watts
http://processorfinder.intel.com/scripts/details.asp?sSpec=SL6WT

Prescott 3.0e/FSB800 (90nm 1MB cache) 89 watts
http://processorfinder.intel.com/scripts/details.asp?sSpec=SL7E4

Now, 20 more watts shouldn't make a difference to the PSU. But
the fan on the processor could be spinning faster than the fan
on the old one. Intel P4 fans are controlled by the air temp
passing through the fan, so a higher case temperature will make
them speed up.

Many PSU fans are also variable speed. They are thermally controlled
in some manner. Generally the PSU fan spins too slow for its own
good.

Asus COP (CPU Overhead Protection) is something added to Athlon
boards, because Athlons had no burnout protection. Asus uses a
Winbond chip or an Attansic chip, to sense the diode temperature
inside the CPU. These chips have a shutdown signal, for when
the CPU gets too warm. Since Asus had to add a chip, and a
small additional expense to each board, they apply their marketing
term (COP) to the adverts.

In the case of your new Pentium chip, there are two levels of
protection. There is thermal throttling, where the CPU does
less computing, if it gets too warm. This cuts in at maybe 70C.
A second level of protection is a 135C or so, and at that
level, the processor uses a shutdown signal to stop the thermal
problem. Since these features are part of the processor, they
don't need an Asus marketing term applied to them.

You could check the hardware monitor in the BIOS, to see what
temperatures are listed for stuff. Or use MBM5 or Asus Probe,
to check temperatures while running Windows. I have a 2.8GHz
Northwood, and sitting idle in Windows, it draws maybe 13 watts
or so (measured via ammeter on the 2x2 ATX12V connector). I
expect your Prescott will have a higher idle power draw than
that.

In any case, if it really is the PSU fan you are hearing and
not the CPU fan, better have a look around. The shutdown could
be the PSU itself shutting down on overheat. Feel the case
of the PSU, feel the air exhausted from it, to determine whether
the PSU is under stress.

Otherwise, I think you are on the right trail. Either the CPU
isn't seated right, or something is shorting in the case. You
could try the "cardboard test", running the motherboard outside
the case, to see if the problem stops. Without other equipment,
it is pretty hard to figure out where the extra power is going,
or if there really is a lot of extra power being drawn.

A long time ago, there was a problem with the P4C800 deluxe
- see the post by Mechabouncer in this thread. This only applies
to the first few thousand boards. The solder short
is somewhere around the plastic stiffener for the CPU, on the
underside of the board. The picture is with the plastic part
removed, showing how the hot solder got distorted enough to
touch an adjacent solder joint.

http://www.techsupportforums.com/showthread.php?s=&postid=41955
http://web.archive.org/web/20040227200251/http://koti.mbnet.fi/~nightops/eki/DSC00249.JPG

HTH,
Paul
 
You made NO MENTION of which version of the 3.0 GHz processor you wer given
and installed. If it's a Prescott version then you can expect the power
supply to work considerably harder. The Prescott CPU puts out about 30%
more wasted heat than the older Northwood version. And as the case heats up
inside, power supply units put out LESS available wattage. They are
operating temperature dependent.
 
Paul

Thankyou for taking the time to post such a detailed and informative
reply. You have given me plenty of information to try and track down
the problem. I really appreciate that. Thanks
 
Back
Top