We will discuss below some specific techniques for achieving this in Pentium-based systems. Multi-channel voltage, temperature and fan-speed monitoring, together with programmable limit-setting for each of these parameters, goes a long way towards meeting the monitoring and control objective. Replacing a fan for $10 is more appealing than replacing a $1000 CPU or an even more-expensive system board. When the speed has decreased by 10 to 15% from its nominal speed, the software can note the problem and shut down the system before the deterioration has caused additional damage. For example, a clogged-up cooling fan may be detected by monitoring its speed. Impending failures can be detected, the sources identified, and corrective action taken - or even system shutdown invoked - before expensive damage occurs. All the vital functions are monitored continuously and the results communicated to the systems management software. By controlling fan speed, greater efficiency, reduced power dissipation and lowered noise levels are achieved.Īnother important area that benefits by effective hardware monitoring is total cost of ownership (TCO). Temperature sensing, often coupled with fan-speed monitoring and control, are a couple of the techniques being employed today to ensure system reliability. As ICs and systems become increasingly faster, more complex, and more dense, removing the excess heat and maintaining safe, reliable operating temperatures has become increasingly important. Simple voltage-comparator types of circuits can be used to monitor fixed supplies but monitoring variably loaded high-accuracy supplies requires more sophisticated solutions involving analog-to-digital conversion of voltage levels.īesides tightly controlled operating voltages, many of today's systems also rely on thermal management approaches, such as the cooling provided by active heat sinking, convection cooling and forced air cooling to maintain reliable operating conditions. In order to maintain long-term reliability, all these voltages must be accurately monitored and controlled. In addition to the requirements of the processor chip, a typical system will require at least 4 other regulated supplies, +12V, -12V, +5V, and +3.3V, for other functions, such as disk drives, video circuitry, PC cards etc. Controlling the voltage to this degree is not a trivial requirement when one considers the dynamically varying nature of the currents flowing through the resistance and inductance of the printed-circuit-board (PCB) traces. The actual voltage required depends on a number of factors. Instead, the Pentium core logic demands digitally adjustable voltages ranging from 1.3 to 3.5 V with 50-mV resolution. The newest Pentium II microprocessors running with clock rates in excess of 450 MHz require complex, highly regulated supply voltages - a simple +5 or +3.3-V power supply no longer suffices. The latest generation of Intel Pentium-based products clearly demonstrates the importance of hardware monitoring and control. System performance can be maximized by closely controlling these parameters to remain within tight limits so as to maintain optimum operating conditions for the circuitry and avoid reduction of component life. The feedback portion of the control loop is accomplished by hardware monitoring - the continuous measurement of critical system parameters, such as power supply voltages, internal temperatures, cooling fan performance, and other environmental factors. Examples include the need to maintain accurate supply voltage levels and continually dispose of the heat generated by high-performance chips. We will consider techniques for making accurate measurements and offer solutions for the range of hardware monitoring tasks in Pentium II-based systems as embodied in the ADM9240 chip.Īs designers of ICs and systems seek to squeeze every last morsel of performance out of their designs, hardware monitoring and control have become an integral part of circuit board design objectives. This article will focus on accurate voltage and temperature monitoring as well as serving other hardware monitoring requirements. Management of the electrical, mechanical, and thermal environment is of growing importance in today's microprocessor based systems.
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