I am sure many of you are familiar with the importance of proper cooling, especially when overclocking your system. But let us spend a few minutes to look into exactly how and why supercooling your processor works.
One of the most obvious reasons for cooling your processor when overclocking is the increased generation of heat. There are two reasons for the increased heat production – the first is simply that the faster your processor runs, the more heat is produced, and the hotter and faster your processor run, the more problems regarding stability you will have. The second, and in fact the main cause, for increased heat production is increased supply voltage (V).
The relationship between maximum operating frequency and supply voltage.
This figure shows us the relationship between maximum operating frequency and supply voltage. The maximum operating frequency is proportional to (Vth-V) 1,25/V, where we assume Vth is 0,6V. Between 1V and 3V, the operating frequency is approximately proportional to the supply voltage, meaning that if your processor does 2GHz at 1,5V you will most likely make it run at about 2,5GHz to 3GHz when you increase its core voltage to 2,0V.
Increasing the core voltage automatically means higher wattage output of the chip -- doubling the voltage means doubling the frequency potential, but it also increase the total wattage output by about 800%. If a CPU that originally emit 90W it will at double voltage and speed now radiate 720W of heat!
Not only will higher temperatures give you problems with stability, but it will also accelerate Hot Carrier Injection(HCI) aging and electromigration, which in the end drastically reduce CPU life time.
The other reason why you should cool your processor is based on simple semiconductor physics – the efficiency of semiconductors increase as the temperature is decreased.
Simply put, processors are made of a silicon substrate: wafers on which layers of copper used as conductors, and metal oxides used as insulators, are doped to create the circuitry. This technique is known as Dual Damascene, and was in fact introduced by IBM as early as 1984 (one can only wonder what took them so long to implement the Dual Damascene for commercial use).
The process used to make today’s CPUs is known as CMOS, Complementary Metal Oxide Semiconductor CMOS technology. One of the characteristics of semiconductors made with this process is that they become more efficient as we lower their operating temperature. For example at –120C the efficiency of a CMOS CPU actually doubles -– at least in theory.
This also applies to devices cooled less aggressively, so cooling a CPU to –20C will give us an increase by about 20%. Now, 20% may not get you overly impressed, but supercooling the processor in addition to an increased supply voltage will get you a substantial increase in efficiency.