ADI's part (and the earlier device from Maxim Integrated Products) improves the accuracy and responsiveness of temperature-monitoring circuits by bypassing the temp sensor ordinarily attached to the CPU's heat sink. In throttled systems, it could squeeze out additional clock cycles, ADI told me at the time. The Intel reaction seemed to be one of feigned indifference, as if the designated Intel spokesperson couldn't be bothered to discuss "thermals."

The truth is, system-monitoring circuits-temperature sensors, fan controllers, even microprocessor supervisory circuits-are a big business. I'd guess there's at least $650 million worth of business out there, and that National Semiconductor, ADI and Maxim collectively have about a third of that.

The volume on system controllers and microprocessor supervisory circuits is actually quite substantial. One of Summit Microelectronics' app notes, for example, describes how a power-on/reset controller is used to first bring up the tuning control processor in a consumer television set, and then the display control processor. Summit's supervisory circuits cannot be very expensive, but if you ask how many TV sets are shipped each year, you begin to see the volumes involved.

Companies like National and Analog Devices are betting that the faster clock speeds associated with the Pentium and the AMD Athlon will raise their temperatures along with the need for system monitors.

National recently showed a variation of the diode-monitoring circuit using two external transistors (2N3904s) at different temperatures to read airflow. It forms the basis of a contactless fan speed controller-one that could be ramped up and down to cap both heat and power consumption.

Apart from Intel, Analog Devices get its name out there. ADI is a proud sponsor of the San Jose Sharks. Every time local television cameras show the Sharks' dugout, there is the ADI logo.