Doktoraty Wydziału IET

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Increase of Integrated Circuit Efficiency with New Cooling System

Adama Samake

Supervisor: prof. dr hab. inz. Andrzej Kos

Due the fact that increase of data processing efficiency is one of the most important problems occurring in contemporary processors, the technology has been scaling down. particularly for microprocessor, technology scaling is higher than power scaling. Owing to that reason, each new generation of processors experience high power density increase. This has direct relation to on-chip temperature augmentation. Since the limitation of data processing speed is caused by excessive on-chip temperature, the main goal of designers and researchers is focused on finding an optimal equilibrium between throughput increase of integrated circuit and stays under thermal constraint. This means integrated circuits operates as fast as possible without violate thermal policy. In order to achieve that goal, the on-chip temperature should be controlled in a manner that it stays as close to the permissible limit as possible with minimal fluctuations. In this thesis temperature reduction methods for integrated circuit are proposed. Different approaches have been investigated: optimization of high-performance microprocessor topography, throughput enhancement and temperature interval reduction techniques for integrated circuit. The first part of this thesis focusses on solving the optimisation problem of thermally significant elements placement inside integrated circuits. The quasi-optimum location of active modules (heat sources) in two-dimensional processor is found using simple heuristic approach. It is taken into consideration Intel Ivy Bridge processor to simulate the temperature distribution for original published floorplan of Ivy Bridge processor and the floorplan obtained from mentioned heuristic approach. The results show that optimized floorplan can reduce on-temperature gradient by 17% compared to original floorplan of Ivy Bridge microprocessor. Moreover, using heuristic approach plenty possibilities to rearrange different units in microprocessor can be done. In the second part of this thesis, a simple and effective method of ICs’ throughput improvement is developed. It is called TΔT thermal control technique. It does not require any micro-architectural change of integrated circuit. The only modification is attachment of an additional temperature sensor at heat sink boundary. Hence, this enables evaluation of cooling condition change size and quick reaction to dynamic changes in surrounding environment. Therefore, the throughput of chip is improved by optimally controlling on-chip temperature using additional knowledge about surrounding environment. Thanks to the proposed thermal control technique approach it is possible to increase a microprocessor throughput even in 7%. Additionally, the impact of different elements on chip throughput under TΔT technique is evaluated. The results reveal that the interval of time during which TΔT control technique is fed by the information about changes in cooling condition and the period during which the on-chip temperature stays almost constant when thermal control is switched to it (TΔT control technique) are function of different parameters such as heat sink material, ambient circumstance, cooling efficiency, power generated in die etc. Finally, the technique of uniform temperature distribution over integrated surface is presented. It uses chip power consumption-power supply of Peltier heat pump and fan close feedback loop to keep the on-chip temperature fluctuation as low as possible. The thermal control technique offers cooling energy consumption reduction and less reliability issues. It is important to underline that the obtained advantages have direct impact on the improvement of data processing efficiency.

Krakow, 11/06/2018