Dell Optiplex 955 desktop – CPU/heatsink installed using Arctic Silver 5 - 150+ hours run time.
Q9550 cores running at around 53 degs C when the CPU load is under 10% (multiple windows open). Ambient temp. 25 degs C

Added small rear exhaust fan (the stock computer does not come with a rear exhaust fan)
Q9550 cores now running at around 49 degs C when the CPU load is under 10% (multiple windows open). Ambient temp. 25 degs C

For reference: Dell Optiplex 955 desktop E6750 dual core – cores run at around 40 degs C under similar conditions. Ambient temp. 25 degs C

I feel that the Q9550 should idle around 40 degs. – what are your thoughts and suggestions to lower the temps? Ambient temp. 25 degs C - Are the Quads just a hotter running processor?

Thank you in advance.
Update: Today.

I just finished re-seating the CPU/heatsink assembly, and while I was at it, I replaced the CPU fan with a new one.

The fan noise seems unchanged. The CPU temp is still around 50 degrees idling at less than 10% load.

Is the Q9550 a hot running CPU?
what form factor is that Optiplex 755?
with my Opti 745 Slim Desktop I reversed the fan on the stock Dell HSF to blow out of front of case instead of into case like Dell has it
dropped temps by about 5-7C

also idle temps dont tell me anything
Intel admitted to a problem with the DTS (digital temp sensor) that showed a big variance in temps the farther you got away from TJMax temp

to quote "In a previous report on the August IDF presentation in San Francisco, Tom’s Hardware discussed how the information provided by Intel had very little real-world value. The reason Tjunction Max (the temperature where thermal protection is engaged) is not the silver bullet for 45nm Core 2 processors is because the sensors suffer from extremely high amounts of "slope error," that is, they become less accurate as the real temperature moves further from Tjunction Max."

you need to do max load testing to really get idea how good your cooling is
I know in the past you have said that you dont stress test but in this situation run Prime 95 for about a half hour to check load temps

I hope this helped :)
cmon Mal you know that Dell Optiplex 7xx series especially the half height desktop and the small form factor had horible cooling
they have the fan blowing over the CPU into the case across a NB heatsink and a discrete GPU If you have one
I added an exhaust intake 80mm and reversed the the fan in the Dell HSF (realy easy to do) so it flowed from rear to front

to quote jtt283
"I'm not sure how competent Dell cooling is... An aftermarket HSF may give better results. I remember my Q9450 being a little warm, but it wasn't over 50C...perhaps 43C?"

his Q9450 was only about 5-7c lower at idle
very similar CPU probably in a custom rig with better cooling

I might not know high end custom parts that well but I do know OEMs
also I have never seen a CPU partially work in 30 years of owning computers and fixing computers
a CPU either works or doesnt
they are designed to last minimal ten years as per D.O.D. specs
that cpu wasnt overvolted or OCd

Ubrales didnt mention anything about BSODs or crashes to suspect a bad CPU
just crappy OEM cooling IMHO

this is said with all due respect Mal
if it is possible to throw that CPU into another LGA775 tower it cant hurt but first I would suspect poor case cooling before a faulty CPU


I agree. And it is extremely difficult if not impossible to install an after-market heatsink. That was one of the first things I considered.

Dell Mini tower case. Did run p75; the standard 10 minutes sensor test in RealTemp. Full load (100%) temps were 68 degrees.
sorry but I didn't read that posting above from 'smp' in too much detail or the link, no disrespect but I'd like to know about the history of the chip itself first.
how long have you had it and where did it come from.?

when a chip idles that high for no apparent reason usually means that it has ran it's course and actually is now a working malfunctioning chip.
I have seen it before.
chips die or act differently all the time.
try the CPU in another rig to rule out determining factors, CPU or motherboard.
while you take the chip out inspect for any scarring or discoloring as well.
Got this computer from Dell Auction. Except for this high idle temp, the CPU runs fast!

When I re-seated the CPU/heatsink 2 months ago, I took some digital pics of the CPU. Didn't notice any discoloration; nice matte SS surface; looked like a 2b mill finish.

Yes I can try this CPU in another Dell Optiplex 755, but that will be sometime towards the end of June. As I am typing this (12 windows open) the CPU load is 8% and the temp is 48 degrees C.

The air coming out at the back of the case (mini tower) does not feel warm. I added a 80mm fan at the back to assist in air flow.

I checked CPU temps with the side cover off, and it made no difference.