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Technology Stocks : Advanced Micro Devices - Moderated (AMD) -- Ignore unavailable to you. Want to Upgrade?

To: muzosi who wrote (40531)	5/19/2001 3:08:30 AM
From: dougSF30	Read Replies (2) \| Respond to of 275872

Muzosi, great find. P4 Throttling is real. Looks like the published thermal specs are crap. You can run at 1.7 Ghz with liquid nitrogen cooling, but otherwise, be prepared for 850 MHz on average: --------------------------------------------------------- From the Intel P4 PDF: 7.3 Thermal Monitor Thermal Monitor is a new feature found in the Pentium 4 processor which allows system designers to design lower cost thermal solutions, without compromising system integrity or reliability. By using a factory-tuned, precision on-die thermal sensor, and a fast acting thermal control circuit (TCC), the processor, without the aid of any additional software or hardware, can keep the processors' die temperature within factory specifications under typical real world operating conditions. Thermal Monitor thus allows the processor and system thermal solutions to be designed much closer to the power envelopes of real applications, instead of being designed to the much higher maximum theoretical processor power envelopes. Thermal Monitor controls the processor temperature by modulating the internal processor core clocks. The processor clocks are modulated when the TCC is activated. Thermal Monitor uses two modes to activate the TCC. Automatic mode and On-Demand mode. Automatic mode is required for the processor to operate within specifications and must first be enabled via BIOS. Once automatic mode is enabled, the TCC will activate only when the internal die temperature is very near the temperature limits of the processor. When TCC is enabled, and a high temperature situation exists (i.e. TCC is active), the clocks will be modulated by alternately turning the clocks off and on at a a 50% duty cycle. Clocks will not be off more than 3 µs when TCC is active. Cycle times are processor speed dependent and will decrease as processor core frequencies increase. A small amount of hysteresis has been included to prevent rapid active/inactive transitions of the TCC when the processor temperature is near the trip point. Once the temperature has returned to a non-critical level, and the hysteresis timer has expired, modulation ceases and TCC goes inactive. Processor performance will be decreased by ~50% when the TCC is active (assuming a 50% duty cycle), however, with a properly designed and characterised thermal solution the TCC most likely will only be activated briefly when the system is near maximum temperature and during the most power intensive applications. For automatic mode, the 50% duty cycle is factory configured and cannot be modified. Also, automatic mode does not require any additional hardware, software drivers or interrupt handling routines. ------------------------------------------- Explains why Bert & Co. only found the effect on Intel mobos, I suppose. But, the second bold text region is shocking: even WITH a proper thermal solution you can expect certain "intensive" applications to trigger the 50% performance mode. Nice, Intel, real nice. Now we know why they called a component "FireBall" internally. Doug