Patent Application
20070094521
This invention relates generally to techniques for managing heat generation or power consumption in computer systems.
One of the primary problems facing present-day computer designers is how best to manage heat that is generated by the one or more central processing units or other microprocessors in the computer. As circuit density, core voltage and switching speeds increase in a microprocessor, heat generated by the chip also increases. Consequently, many microprocessors are equipped with a heat sink and a fan so that this heat can be transferred efficiently away from the chip die in order to keep the microprocessor within its factory-specified temperature limits.
Another technique that has become known is to equip the microprocessor with an on-chip thermal management system, the effect of which is to throttle some or all of the microprocessor's operations as necessary to maintain a safe die temperature. For example, some microprocessors manufactured by Intel Corporation (“Intel”) exhibit three modes of operation: a normal mode and two thermal management modes called TM1 and TM2. In the normal mode, the microprocessor runs continuously at its full clock speed. In the TM1 mode, the microprocessor runs at its full clock speed but not continuously. Instead, the microprocessor's internal clock is halted periodically according to a fixed duty cycle. In the TM2 mode, the microprocessor's core voltage and clock speed are reduced.
Universally, microprocessor thermal management modes such as TM1 and TM2 have been invoked responsive to a measurement of temperature made with a temperature sensing device such as a thermistor or a thermal diode. For example, the above-mentioned thermal management systems from Intel include on-chip temperature sensing circuitry that functions automatically to place the microprocessor in a thermal management mode when the die temperature has reached a predetermined limit. When such a thermal management mode is active, the microprocessor asserts an externally-visible signal called “prochot” so that external systems may respond appropriately. When the chip's thermal management system becomes inactive, the microprocessor unasserts prochot.
The prochot signal is bidirectional. It not only indicates when the on-chip thermal management system has been invoked internally, but it also can be asserted by external systems to force the on-chip thermal management system to become active. This bidirectional aspect of the prochot signal was provided by Intel so that a microprocessor could be throttled by a temperature-sensing voltage regulator controller that measures the temperature of a voltage regulator system external to the microprocessor. Should the temperature of the voltage regulator system become too high, the voltage regulator controller may assert prochot on the microprocessor in order to reduce the microprocessor's demand for power temporarily, thereby reducing the temperature of the voltage regulator.
Computer 100 also includes a power supply 106 and at least one power supply conductor 108, 110 configured to supply the power requirements of microprocessor 102. A current-sensing power controller 112 is coupled to power supply conductor 108 or 110, and to thermal control input 104. In most computers, a voltage regulator 112 is also present and is disposed between power supply 106 and microprocessor 102 as shown in the drawing. In such computers, current-sensing power controller 112 may alternatively be coupled to power supply conductor 110 in lieu of power supply conductor 108 without deviating from the scope of the invention as claimed herein. It is common in such computers, however, for microprocessor 102 to be able to request varying supply voltages from voltage regulator 114 using signals 116. Therefore, the configuration shown in the drawing is believed to be simpler to implement, as the voltage supplied at output 118 of power supply 106 and received at input 120 of voltage regulator 114 is normally a constant value within a small tolerance.
The behavior of current-sensing power controller 112 is to assert thermal control input 104 when current flow in power supply conductor 108/110 exceeds a first threshold value. The result will be that microprocessor 102 will reduce its power requirements and consequently its temperature. Current-sensing power controller 112 may be further operable to unassert thermal control input 104 when current flow in power supply conductor 108/110 falls below a second threshold value lower than the first. This style of operation is visualized in
Current-sensing power controller 112 may take a wide variety of forms without deviating from the scope of the invention as claimed herein. Such forms will be apparent to those having ordinary skill in the art and having reference to this specification. For example, numerous methods are known for sensing current flow in a conductor, including lossy methods utilizing one or more components in series with the conductor, as well as so-called lossless methods that utilize electromagnetic sensing techniques such as hall-effect devices and transformers. Any of these or similar techniques may be employed when implementing a system in accordance with the invention. One simple and inexpensive implementation is illustrated in
In the embodiment of
For the implementation shown in
In alternative embodiments, the values of one or both of thresholds 200, 204 may be determined programmatically by writing a data value into a configuration register 122 (referring again to
One of the advantages of the invention over temperature-sensing controllers is that the current-sensing embodiments of the invention can be implemented more inexpensively than can temperature-sensing controllers. This is so because embodiments of the invention do not require the use of thermistors or thermal diodes. Moreover, it is frequently possible to sense current using already-existing series resistances such as the FETs found in switching power supplies, which may further reduce the cost of implementation.
Another advantage provided by the invention is that it allows microprocessor power to be controlled independently of microprocessor temperature. The relationship between microprocessor power and temperature varies from one microprocessor family/model/stepping/frequency to another. Thus, the ability to control microprocessor power independently of microprocessor temperature is valuable, since numerous different microprocessors may be installed in the host computer without changing the design or even the settings of the thermal control system of the invention.
While the invention has been described in detail with reference to preferred embodiments thereof, the described embodiments have been presented by way of example and not by way of limitation. It will be understood by those skilled in the art that various changes may be made in the form and details of the described embodiments without deviating from the spirit and scope of the invention as defined by the appended claims.
