1. Field of the Invention
The present invention relates to a data processing device with a cooling fan to prevent the temperature rise of the processor performing data processing.
2. Description of the Related Art
Conventionally, in order to perform stable data processing it has been necessary to prevent temperature rise in processors formed from semiconductor. For this purpose a cooling fan has generally been considered appropriate.
Further, as a conventional art, a technique where the temperature rise in the package of semiconductor circuit is suppressed to prevent thermorunaway is disclosed as shown for example in Japanese Patent Laid-Open No. 2004-6446 publication (paragraphs [0048] to [0052], [0059], FIG. 3). This technique is to detect the temperature of a function module substrate as an electric signal, to control the frequency of the system clock signal of the processor by using the detected signal, and to control the processor such that it operates at the maximum speed at which thermorunaway does not occur. Specifically, a temperature monitor is provided to detect the temperature of the substrate or a predetermined region of the substrate. The temperature monitor makes use of the temperature characteristics of the transmitting frequency of a ring transmitter. The ring transmitter is a transmitter with odd numbers of inverting amplifier circuits connected in a ring state, and its transmitting frequency is determined by the operating speed of transistors that constitute each inverting amplifier circuit. The operating speed of transistor has the characteristic that it becomes faster as the temperature of a junction surface gets lower and it becomes slower as the temperature gets higher. The temperature of package is monitored in this manner, and when the temperature reaches the reference temperature, the operating state of the microprocessor is changed such that the power consumption of the microprocessor is limited to a predetermined value.
Further, as a conventional art, a technique is disclosed in which the load state of the processor is detected to distinguish whether or not interruption conditions are satisfied and the optimum processing can be executed based on processor load, as shown for example in Japanese Patent Laid-Open No. 11-345135 publication (paragraphs [0009] to [0015], [0026] to [0041]). Processor load factor is detected by this conventional art. In this detection method, since idle signals are output when no processing is executed inside the processor, that is, during an idle period, the idle period ratio in one measurement period is found by measuring the idle signals for a predetermined time by using the idle signal and a processor clock, and the processor load factor during the predetermined time is found from the result. The processor is designed to activate on a data processing state based on the processor load factor.
However, in the conventional art shown in the above-described Japanese Patent Laid-Open No. 2004-6446, since its construction is such that the detection section for detecting temperature is fixed on the substrate, it is necessary to specially prepare the detection section and to assemble it on the substrate. Further, the substrate temperature does not only depend on the operating state of the semiconductor integrated circuit but is also affected by the environment inside the electronic device in which the circuit is arranged. For example, when electronic parts with a large calorific power are closely arranged, the substrate temperature is largely affected by the calorific power of the electronic parts, and it becomes impossible to accurately detect the temperature of the processor itself. As a result, the substrate temperature is higher than the processor temperature, and suppressing the frequency of the system signal of the processor based on the measured result of the temperature means that the processor is allowed to operate on a significantly low state compared to its optimum function. Therefore, there has been a problem that the processor has not always been used at an appropriate efficiency. Although it is natural to consider frequency correction, setting the correction amount accurately in advance is problematic.