Phenom II 955 BE internal throttling due to junction temps?

[Knowledge8069]

I'm wondering if anyone has ever overclocked a CPU and had the chip throttle itself due to internal temps, even though the outside case of the CPU itself was below max temp. I'm referring to the case temp being below max rating, but the internal junction temp reaching its maximum.

 

While overclocking my Phenom II 955 Black Edition processor, I was able to get it to 4.3 GHz. It passes stability tests and does not blue screen during daily usage. Running OCCT and Intel Burn Test, I noticed that after 2 mins of stress testing the multiplier will drop to 8 and the cores will run at only 800 MHz for a few seconds before returning to 21.5 multiplier (4.3 GHz). The outside case temp of the chip according to Core Temp and Speed Fan is never hotter than 57 C. Max case temp for the CPU is 62 C, so the temps I'm seeing are a few degrees under the max.

 

I'm using a Zalman CNPS10X Performa cooler. Vcore is 1.49 V and CPU/NB is 1.35 V on an ASUS M4A87TD EVO mobo. Cool n Quiet and C1E are disabled.

 

What I think is happening is the heat sink system is able to pull enough heat away from the outside of the CPU, but the internal temps are building to the point that the chip throttles itself down to prevent burning up. It seems that the CPU cannot get heat to the outside of itself fast enough to prevent it from overheating, even though the heat sink and fan are doing more than enough. Has anyone else had this experience? Is it correct that the internal temps are just too hot even though the CPU case temp is within spec?

Edited March 28, 2011 by Knowledge8069

[Waco]

While overclocking my Phenom II 955 Black Edition processor, I was able to get it to 4.3 GHz. It passes stability tests and does not blue screen during daily usage. Running OCCT and Intel Burn Test, I noticed that after 2 mins of stress testing the multiplier will drop to 8 and the cores will run at only 800 MHz for a few seconds before returning to 21.5 multiplier (4.3 GHz).

Do you have Cool-n-Quiet enabled? It's entirely likely that you're seeing the momentary drop in CPU load when Linpack (OCCT, IntelBurnTest) finishes a run and starts a new one. I know my Core 2 Quad has just enough time to throttle down to the minimum speed for a second or two right before jumping back up to max speed.

[IVIYTH0S]

Do you have Cool-n-Quiet enabled? It's entirely likely that you're seeing the momentary drop in CPU load when Linpack (OCCT, IntelBurnTest) finishes a run and starts a new one. I know my Core 2 Quad has just enough time to throttle down to the minimum speed for a second or two right before jumping back up to max speed.

This sounds logical to me, and has indeed happened while running IntelBurnTest to me a couple of times