Hot to the touch .... warm to the touch?

[AluminumStudios]

I have an Epox 8K3A+ motherboard in an Antec case with penty of internal circulation (1 fan in front, 2 in back + 2 in power supply). My hard drives and the inside of my case are cool to the touch and my system temp is usually around 29 c.

I had a Thermaltake Volcano 7 and now have a Thermalright SK-7 that I put an 80 mm Antec smartfan on (it was all I had at the time.) The smartfan varies between 4000-5000 rpm usually.

Now to the meat of this post ... I have never been able to accurately interpret my CPU temperature readings. I have an Athlon XP2200 (tbred-a) overclocked a bit to around 1908 MHz. My motherboard reads from the CPU core which would be around 61 idle and get near 70 c under a load. The heat sink itself never felt hot to the touch, only warm ... even around it's big, solid, copper base. I updated my bios to a version that I found that reads from the socket temp sensor. My system now reads 40'ish idle and 50 c under load. Compared to many numbers I see posted by people this still seems very high ... however my heat sink does not feel burning hot to the touch like I would expect it to. It only feels warm.

My 2nd computer is a slot1 PIII-500 (old Kaktmai.) It's heat sink gets so burning hot it almost leaves grill marks on my fingers from touching it ... it's insane. I have a thermistor glued to the heatsink and that system reads 56c. I find it hard to believe that a difference of 6 deg. celcius could account for th scorching heat I feel coming from my PIII vs the warm to the touch heat sink of my Athlon ...

Things I've checked and recheced:

Both heat sinks are on in the proper orientation.
The PIII heat sink is using generic radio shack silicon thermal compound. I tried that on my Athlon as well as CompUSA (possibly made by Antec?) silver compound - I had the same results with both.

I've also re-applied the compound multiple times trying both a lot and a little ... the results never varied by more than just a degree or two.

So, why are my Athlon temps so high while the heat sink feels barely warm?

 

[jarsoffart]

You have to glue the thermistor closer to the core of the CPU. I think motherboard manufactueres glue the thermistor under the core.

 

[OulOat]

The base might not have good contact with the CPU core, meaning you might want to lap it or both the core and the hs. Also, why did you change it to a bios that reads the socket temps? Diode temps are accurate and actually mean something. Socket temps change from mobo to mobo making them worthless in comparisions.

 

[AluminumStudios]

It's not a problem with contact. I had an Athlon XP2000+ (which I gave to my mom) and an XP2200+ (which I have now) and a Volcano 7 and an SLK-7 in all possible combinations with the same results each time. The bottom of my Volcano 7 felt as smooth as glass.

So I know I don't have a problem with heat transfer, poor installation, or anything like that.

As far as the thermistor on my Pentium III, it's on the underside of the heat sink near the core. the entire heat sink gets so bloody hot I can't hold a finger to it (anywhere on the heat sinnk) for more than a second or two before it burns. I'm wondering why my Athlon is reading similar temps, but it's heat sink barely feels warm to the touch.

I changed to a bios that reads socket temperatures so I could compare with many other people who get temps from their sockets (mobo manufacturers were slow to read temps from the Athlon core.) Plus I simple got sick of seeing my temps at 69 c. when running AfterEffects. 50c looks better

For everyone else who has Athlons ... how hot do your heat sinks feel? Do they burn if you touch them, are they just warm to the touch?

 

[OulOat]

It doesn't matter so much as whether or not it's smooth but is it flat. The problem might be the hs's aren't flat, or your cpu core isn't flat. Also, you did remember to completely clean off and reapply the thermal paste each time you reinstall the hs, right?

 

[Bookie]

my results are similar to yours aluminumstudios. I have an 1800+ with the SLK-800 and Vantec Stealth fan (2400rpms). My heatsink is barely warm but my temps range from 40-48C. This is in comparison to the stock hsf that came with my processor at 51-60C.

 

[Fallen Kell]

Do NOT LAP YOUR CPU! I will repeat DO NOT LAP YOUR CPU!!!

Current CPU's are laser cut to be perfectly flat and level. All lapping can do is increate the scratches on the CPU allowing for more air. It may also damage the current line of CPU cores as they have circuitry very near the top layer of the core.

Lap your heatsink if you want. Lap your northbridge or southbridge, even possibly lap your old graphics card chip (not the current ones though), but do not lap your CPU.

 

[AluminumStudios]

I've been working on computers long enough to realize that lapping your CPU is silly and as far as I can tell everything is all flat. I even stopped using my CPU shim to make sure of it.

But now that I have 485 grams of copper (185 grams over AMD's weight limit spec) crushing down on my core I kind of wish I had left it in

Anyway, I was hoping for more than the standard "make sure it's level, etc., etc." I've been working on computers long enough to know ... but hate always having to explain that I"m not a n00b.

Oh well, I guess I"ll fall back on my old philosphy - as long as it's stable and I don't smell anything burning it's ok ....

 

[OulOat]

You lap a CPU core by putting some "grinding" compound (forgot the real name) inbetween in CPU core and hs and then proceed to twist around (so I read). This will sand both the core and the hs so they perfectly match each other. The downfall to this is you can't switch HS's unless you want to grind some more and risk killing your cpu. Eh, never tried this since I'm poor, but there are some tuturials on this.