CPU cooling

IF YOU WANT A FAST, RELIABLE COMPUTER, HEAT IS THE ENEMY. DARIEN GRAHAM-SMITH EXPLORES WHY THERMAL MANAGEMENT IS SO IMPORTANT, AND HOW TO KEEP YOUR OWN PROCESSOR RUNNING COOL

The CPU in your phone, tablet or computer processes billions of operations a second. On the microscopic scale, that means opening and closing billions of tiny electrical gates. This is done using electrical energy – and, as you may recall from physics class, no electrical process is 100% efficient. Every time a transistor is activated, a small amount of energy is lost as heat.

Is this a big deal? In isolation, no. The heat generated by the operation of a single transistor is minuscule. No chip manufacturer publishes this figure; we suspect it would be difficult to even estimate on such a tiny scale.

However, with billions of operations per second going on across billions of transistors, the heat can quickly build up, causing a significant proportion of the chip’s area to become measurably hotter. In fact, that’s an understatement: without some sort of thermal management, the internal temperature inside a typical desktop CPU would easily go well beyond 100°C in everyday use.

Exactly how much heat a chip will generate – and how quickly – depends on a variety of factors. One is exactly how fast it’s running, as running more operations per second naturally leads to a quicker build-up of heat. This is why overclocking is considered a risky business, and why enthusiasts often invest in souped-up coolers, as we’ll discuss below.

The complexity of the task is a factor, too. Chunky workloads such as video editing and AI processing can light up dozens of cores at once, while many desktop programs run largely on a single CPU core – meaning a large portion of the chip is left sitting idle, and cool. In fact, modern chip designers aim to completely power down unused chip areas whenever they’re not in use, partly to reduce power consumption but also to minimise heat buildup.

THERMAL THROTTLING ISN’T AS BAD AS A CPU CRASH, BUT HAVING YOUR WHOLE SYSTEM SLOW DOWN ISN’T GREAT

This brings us to the final factor: the physical make-up of the chip itself. All things being equal, a chip with a billion transistors will generate more heat under load than a simpler design. Hence, chips intended for thin and light laptops, which have limited cooling capabilities, tend to use simpler designs with fewer cores. Desktop processors can afford to pack in more silicon, while server hardware typically uses large complex chips with high core counts and fast clock speeds, relying on high-powered external cooling systems to prevent overheating.