No thermal sensors on Intel CPU. How can that possibly be?

I am thinking the BIOS doesn't support this CPU, which suggests that replacing the new CPU is the only solution. And I'm surprised the Pentium D outperforms the E6300.

A lot of Dell systems don't detect CPU thermal sensors.  The CPU fan typically has a temp sensor in it.

The E520 has an ambient air-temperature sensor connector and a Processor Fan connector on the motherboard. Did you (accidentally) disconnect one of the sensors from the motherboard when you replaced the CPU?

Reboot and press F12 to open BIOS setup. Go to Utilities partition and run the fan tests. If the fan fails, replace it with an OEM Dell fan that's designed for this model. BIOS won't detect a non-Dell fan because it doesn't have the sensor, meaning you'll get a error message at every boot.

Thank you for your reply.

That's interesting that the Dell BIOS 2.4.0 may not support the Intel SL9DA Pentium D 2.80GHz 4M 800 Socket 775 Processor.

I found this list of BIOS 2.4.0 supported CPU's which include the following

"Conroe, E6400, 2.13G
Conroe, E6700, 2.66G
Conroe, E6300, 1.86G
Conroe, E6600, 2.4G
Prescott P4, 541, 3.2G
Prescott P4, 524, 3.06G
Prescott Celeron, 351
Prescott Celeron, 346
Prescott Celeron, 336
Prescott P4, 531, 3.0G
Presler P4, 940, 3.2G
Presler P4, 945, 3.4G
Presler P4, 930, 3.0G
Presler P4, 925, 3.0G
Presler P4, 950, 3.4G
Cedar Mill, 661, 3.6G
Cedar Mill, 651, 3.4G
Cedar Mill, 641, 3.2G
Cedar Mill, 631, 3.0G

Plus the Q6600 and possibly the Q6700."

I believe the Intel SL9DA would be classed as Presler P4 915 which indeed doesn't appear in this list. However, I'm not sure that this list is exhaustive. However, why would it be excluded as it's not that old (CPU SL9DA released 2005, BIOS 2.4.0 released 2007)

Perhaps you could advise me how I can be sure whether my CPU is supported or not as my googling attempts have not yielded a definitive answer. 

Whether or not the SL9DA outperforms the stock E6300 is still up for debate. Certainly the computer boots faster and casual browsing seems brisker. However, I have not stressed the computer nor have I done any benchmarking.

Thanks for your reply and suggestions.

Well, in fact the CPU fan is working perfectly so the absence of CPU thermal indicators has not affected this fan and you have already explained why it shouldn't.

The reason I suspected it wasn't functioning is because its operation has mysteriously become extremely silent. This may well be related to the fact that, when I changed the CPU, I thoroughly cleaned years of dust from both the heatsink and its fan

So much dust was removed that I was looking forward to seeing how much lower the CPU operating temperatures would be. But, alas, no thermal sensors.

So, from suggestions received in this thread, it seems my question now boils down to whether or nor the SL9DA CPU is defective (no or damaged thermal sensors) or whether the CPU is simply not supported by Dell System BIOS 2.4.0

In this regard, I should point out that several CPU operating parameters are picked up and displayed so the BIOS is not totally unsupportive of this CPU. These include the CPU usage and the CPU operating frequency (speedsteps between 2.4GHZ and 2.8GHz which is displayed by the Linux Conky parameter Freq).

So, is the CPU defective or not fully supported by BIOS?

Thanks for any views.

I still don't understand your point. :emotion-7:

If the PC boots normally and runs all your software, it is not defective. If it wasn't supported by BIOS, it wouldn't even boot.

As I already said, Dell systems do not read the thermal sensors on the CPU, even thought some non-Dell system might be able to read them from this same CPU. So no matter what OS you use or what tools you try, you're just not going to get CPU temp readings.

And as I also already said, Dell uses the thermal sensor in the CPU fan to control fan speed, not the CPU's thermal sensors.

Perhaps the new CPU just produces less heat, and/or things are cooler now because you cleaned out all the dust bunnies, and presumably because you put fresh thermal paste on the CPU when you attached the heatsink and that may better dissipate the heat. 

Hi Ron

Thank you once again for your comments and I apologize for not stating my concerns with more clarity.

Yes, the computer boots without problems and runs everything, in a range of OSes (multiboot) without the slightest difficulty.

However, I cannot find an indication of the CPU core temperatures.

No, I do not expect, and never have expected, to see a Dell reading of these temperatures. I'm principally a Linux user and have used lm_sensors (nothing to do with Dell) for this purpose for many years on a variety of computers with many different CPU's and have never ever had a problem reading the CPU core temperatures.

I can even measure the core temperature on a Raspberry Pi  Arm1176JZF-S 700 MHz processor with ease.

The only time I've ever been unable to read a CPU's core temperatures is with this Intel SL9DA Presler 915.

Lm_sensors do not detect any sensors on the CPU in Linux. Neither do Core Temp nor Nvidia System Monitor read the core temperatures.

In my experience, this is very unusual. Indeed, it is uniquely so.

My question therefore is whether this is indicative or not of a hardware flaw or damage on the CPU.

But unless Dell enabled the CPU thermal sensors in BIOS, they're not going to be seen by any software. You can have all the fully functional sensors you want on the CPU but if their output goes nowhere, software can't read what it can't see. 

SpeedFan doesn't see the thermal sensor on the Intel CPU in my Dell desktop, even though SpeedFan sees thermal sensors on the video card and in both hard drives.

This does not mean you have a defective CPU or there's a "hardware flaw". It's just the way Dell does their hardware.

Look at it this way:  If you don't plug your TV into the wall, you won't see a picture, so does that mean it's a defective TV?

You're just worrying about nothing.