4  3  EP 1 499 941 B1 sponder. In particular, the document refers to setting a transistor body bias signal in controlling chip parameters. The body bias signal refers to the relationship between the source voltage and body voltage of a field effect tran- sistor (FET). These transistors are present in a proces- sor. A control circuitry is provided to supply the FET body bias signal as well as clock signals for the processor. The control circuitry receives an indication of temperature from the processor and lowers the clock frequency in response to temperature exceeding a threshold. Also, based on the body bias, the clock frequency can be changed to improve performance. The process for se- lecting the clock frequency and the bias and supply volt- ages is an iterative process involving feedback from the processor (e.g. temperature and current). [0009] Furthermore, from US 5 642 388 there is known a microprocessor clock control circuit and method capa- ble of continually adjusting its frequency based on the current system operating conditions. This circuit com- prise a means for selecting a target operating frequency comprising a selected maximum operating frequency. A first section determines maximum frequency values for various criteria and selects the lowest frequency value thereof as a maximum operating frequency. Further- more, the means for selecting a target operating temper- ature comprise a second section determining a selected minimum operating frequency in the same way as the first section, apart from selecting as a minimum operating frequency the highest frequency between all minimum operating frequencies. A third section selects the select- ed maximum operating frequency or the selected mini- mum operating frequency as target operating frequency after taking a variety of different system conditions (any system activity) into account. Thus, there is performed a complex determination of different maximum and mini- mum operating frequencies and a subsequent selection of a target operating frequency depending on system ac- tivity, which is less or equal than any maximum frequency value determined. [0010] US 5 940 786 discloses a system and method for regulating a temperature of a microprocessor by var- ying the clock rate. The system comprises an oscillator having a frequency which varies based on a temperature of the microprocessor. In case a high temperature greater than a second threshold value is detected the clock fre- quencies are reduced in order to reduce a heat genera- tion and to stabilize the microprocessor temperature. [0011] Finally, US546951 discloses a system and method for regulating the frequency of a microprocessor according to the measure temperature and power supply voltage. The frequency may be increased above the max- imum specified operating frequency of the microproces- sor if the combination of measured temperature and volt- age allows this. [0012] What is needed, then, is an improvement in the art which allows the chip to operate in this valid operating range when operating conditions permit. [0013] The invention will be understood more fully from the detailed description given below and from the accom- panying drawings of embodiments of the invention which, however, should not be taken to limit the invention to the specific embodiments described, but are for explanation and understanding only. Brief Description of the Drawings FIG. 1 shows a voltage regulation system according to the prior art in which a voltage identification signal controls a voltage regulator. FIG. 2 shows a thermal throttling system according to the prior art in which a thermal throttle controls a clock generator as a function of operating tempera- ture. FIG. 3 shows a power management system accord- ing to the prior art in which the clock signal differs according to whether the system is operating on grid power or on battery power. FIG. 4 shows a frequency/ temperature/ voltage anal- ysis and operation according to the prior art. FIG. 5 shows a frequency/ temperature/ voltage anal- ysis and operation according to this invention. FIG. 6 shows one embodiment of a system according to this invention. [0014] FIG. 5 illustrates one mode of operation of the invention. At the worst corner case of minimum voltage V1 and maximum temperature Ttest, the chip will be clocked at maximum specified operating frequency Flim- it, just as in the prior art. However, as the temperature falls below Ttest, the operating frequency is not fixed at Flimit, but can be raised, so long as it does not exceed the limit imposed by the voltage/ temperature combina- tion. This may be done in a series of steps, such as via a lookup table which uses temperature and voltage as addressing or index values and which outputs frequency values. In other embodiments, it may be done using an analog delay element which relies on the same physical properties as the load circuit. [0015] The actual operating range (AOR) is extended to include the area above the Flimit maximum specified operating frequency at which the prior art is limited. Under some circumstances, the system may elect to raise the operating voltage, such as from V1 to V2. This, in turn, will generally permit the frequency to be raised even fur- ther, as illustrated. At temperatures approaching Tjmax, the frequency and optionally also the voltage may be stepped downward to reduce power consumption, lower the temperature, and prevent data corruption or cata- strophic failure. [0016] The skilled reader will readily appreciate that the heavy frequency line shown is but one of countless possibilities. For example, it is not necessarily the case that as the temperature approaches Ttest, the voltage Detailed Description 3