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To: Joe NYC who wrote (74268)	3/12/2002 2:22:21 PM
From: Ali Chen	Read Replies (1) \| Respond to of 275872

Jozef, "if they set the threshold for thermal protection very low" Thanks to wanna, developer.intel.com I failed to find any information on the thermal threshold. The only occurrence of "thermal trip point" is on page 87: "An external signal, PROCHOT# (processor hot) is asserted when the processor detects that its temperature is above the thermal trip point." The point value is not specified. Something is fishy here. As usual. You say: "the chip will be running at half speed most of the time" You may be too generous here. There is a hint on the same page 87, that TCC (Thermal control circuit) automatically operates "by alternately turning the clocks off and on at a duty cycle specific to the processor (typically 30-50%)." Typically? What the heck, is this a specification for a particular processor model, or what? The number 30% is new to me, it used to be 50% for regular P4. So, 30% seems like a good possibility for P4M, :-) Also, in so-called "On-Demand" mode, the duty cycle can be as low as 12% on / 87% OFF, which translates into 200MHz or 212MHz effective operating frequency. The "On-Demand" mode is engaged by software using readings from thermal diode, and therefore can be set arbitrary low. Regards, - Ali

To: Joe NYC who wrote (74268)	3/12/2002 2:48:44 PM
From: Petz	Read Replies (1) \| Respond to of 275872

Looking at the Datasheet for the P4M, I think the 35 degC limit is incorrect. 35 happens to be the temperature for which Intel specifies power consumption for the sleep and deep sleep modes, but, it is in no way a temperature limit for the device. In fact, the P4M can withstand junction temps of 100 but it will go to 30-50% speed at some unspecified temperature below that. Now it may turn out that 35C is about the maximum ambient temp that allows a P4M notebook to avoid an average junction temp over 90C, which would probably put the "hot spots" on the die at 100. DIssipating 30W (probably more, IMO, plus memory, power supply inefficiency, battery heating, chipset, video chipset, etc) inside the body of a notebook makes operation in high ambient temperatures impossible. The spec for maximum thermal dissipation is a real gem, even for Intel: Definition of TDP (thermal design power) page 85: TDP is defined as the worst case power dissipated by the processor while executing publicly available software under normal operating conditions at nominal voltages that meet the load line specifications. The TDP number shown is a specification based on ICC (maximum) at nominal voltages and indirectly tested by this ICC (maximum) testing. TDP definition is synonymous with the Thermal Design Power (typical) specification. The Intel TDP specification is a recommended design point and is not representative of the absolute maximum power the processor may dissipate under worst case conditions. I guess Intel feels that in the English language there is a difference between the phrase "worst case power" and "power under worst case conditions." (It depends on the meaning of "is"?) So they say it is based on ICC (maximum), huh? Well, go to page 23 and you will find ICC max is 29.9 amps at 1.3 volts! That's almost 39 watts, and there are other supply voltages as well. BTW, Intel now says that leakage current is too high to protect the CPU automatically from thermal runaway. Even though it will stop the clock if the temp gets too high, it is required that the power supply be designed to interrupt Vcc if a signal on the processor is asserted. 2.4.3 Catastrophic Thermal Protection The Mobile Intel Pentium 4 Processor-M supports the THERMTRIP# signal for catastrophic thermal protection. Alternatively an external thermal sensor can be used to protect the processor and the system against excessive temperatures. Even with the activation of THERMTRIP#, which halts all processor internal clocks and activity, leakage current can be high enough such that the processor cannot be protected in all conditions without the removal of power to the processor. If the external thermal sensor detects a catastrophic processor temperature of 135°C (maximum), or if the THERMTRIP# signal is asserted, the VCC supply to the processor must be turned off within 500 ms to prevent permanent silicon damage due to thermal runaway of the processor. Refer to Section 5.2 for more details on THERMTRIP#. The P4 NW has a similar paragraph. I wonder how many motherboards use THERMTRIP# to cut Vcc, or do they assume that the clock throttling will be enough protection? Petz