Best place to put a probe

Hi friends, everybody knows that is impossible to put a probe under the block (pentium 4 ).
So where is the best place to put it to get an better accuracy temp ?
the block ?
the mobo ?
thanks

I am also wondering about the placement of temp probe. I'm planning to buy or build my WC setup and trying to use DigitalDoc with it. BTW, I'm noob to WC and this is my first post Thanks advance for your reply and stay cool

You could cut a recess up to where the core area is, on the waterblock - as long as the waterblock has a base thicker than 3mm and/or can stand a recess being milled from it. Just to make it clear, I'm not saying cut any waterblock base away from the core area, just mill a small channel from the waterblock base up to where the die would be under the heatspreader. Then you can use some thermal epoxy to set the thermistor in the small channel - and sand it down to the thickness of the base. I'm assuming you're using those slimline thermistors as well?

I thought you could just read the temp off the chip itself.. Or do only certain motherboards support that? (don't know how it works for intel, thought they all did)

Is this an open ended question?!?!?! hahahahahah Hummmm.... let me see...... were can you put that probe?!?!?!

Sorry I couldn't help it!!!

But seriously, you could drill a hole into the heat sync and place it in there.
Rob

Hmmm, on a P4 if you were daring, you could drill a small hole into the side of the heatspreader and put the probe through the hole getting on or close to the core. On an AMD CPU, the best way is to have the probe touch the side of the core.

nikhsub1, i have almost the same system like you. How much your mbm shows your cpu full temp ?

I did see an article where they cut the plastic socket down a little in one spot so the probe could sit under the CPU. Also if you tape it on the CPU so that the tip of the probe is just touching the core, some probes are thin enough it will sit right under the HSF.

to be honest most of the heat comes from the top side of the CPU anyway. the term. underneath is only really there to give a rough entimate. The best thing would be to do what nikhsub1 suggested, and just carefully glue it in place.
If you're after really accuracte readings then you'll be wanting to use a therocouple which is really accurate and can be much smaller.

mmm, a lot more complicated than what I've thought...
drilling a little hole on a water block seems to be little too risky for a noob like me. I'd better stay with mbm or something similar till I get better with the tool and knowledge. Thanks guys

Overbrazil said:

nikhsub1, i have almost the same system like you. How much your mbm shows your cpu full temp ?

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WEll it all depends on ambient. Right now, I am at 50C load, ambient is 35C though! When I have an ambient of 25C, I am about 39-40C load. It is way to hot here right now...

Wow thats some serious temps nikhsub1! What do you guys do to get the temps in your house, turn your a/c off during the summer? I live in Florida: possibly the hottest, most humid place on earth (I hate living here if you couldn't tell) and my temps are not that bad at all now and its summer! This is my first year on w/c and if what you guys show as hot temps in the summer and cooler temps in the winter/fall then I'm set for good temps then.

nikhsub1 said:

WEll it all depends on ambient. Right now, I am at 50C load, ambient is 35C though! When I have an ambient of 25C, I am about 39-40C load. It is way to hot here right now...

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Man is too hot in LA
Remembered last summer in Rio de Janeiro(41 C), now am at 42 load (ambient 26 C)
i put the probe touching the wb and is marking 28.5C.

hehe i got a good old military saying for how hot it is but its not really apropriate ( though i imagine some of you would like it )

wannaoc said:

Wow thats some serious temps nikhsub1! What do you guys do to get the temps in your house, turn your a/c off during the summer?

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My house is always a nice 73-74F, I run the AC here no problem. My main rig is at my office, which is a small apartment. I do not run the AC there when i am not there, so it gets very hot. I have lots of fans but when it is 95F, not much you can do. I will say that all the machines (10 of them) at my office fold 24/7 and all do fine in the heat. They are all OC'd and most are AMD systems.

The beauty is that I know my main rig (the one in the sig) can handle 35C + ambient temps and not crash at all. The CPU does not throttle at all either, I monitor my machines remotely via VNC.

Any diode inside the chip will be far more accurate than a thermal probe placed outside the chip. Think about it, how accurately can you tell the temperature of an oven or a refrigerator with a thermometer mounted outside on the door? For more info read Why Many Thermal Measurements Are Not Valid.

Here's an interesting heatsink round up that illustrates the point.

Somehow or other, but the main conclusion is this: for hardcore overclocking, the readings of external thermal sensor are absolutely useless since they don't reflect the factual processor core temperatures.

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You may find Temperature Sensing Technologies a good read too.

Now that we have figured out the best place to read the temperature is inside the CPU die, another problem pops up. With PII and PIII CPUs, the sensor was in the hottest part of the chip. Here's what Intel has to say about PIII diode placement. With P4s and Athlons the diode is no longer in the hottest part of the chip. A little more reading from Intel on the subject. We have the same problems measuring temperatures inside the core when the diode is not in the hot spot as those outlined in Why Many Thermal Measurements Are Not Valid.

The only accurate CPU temperature measurements are from PII or PIII internal diodes provided you have a motherboard that can read the internal diode. There is no way for the end user to get an accurate temperature reading from an AMD CPU or a P4.

Furthermore for those of you with P4s, if you consider the last link from Intel, your CPUs are most likely throttling more often than you may realize.