March 22, 2010

Heat and the CPU

When I established this blog, I expected that a large proportion of my posts would involve computers. Somehow, that never came to pass. That makes this post an exception.

I have seen many problems with personal computers over the years. More often than not, software is responsible, whether code in the operating system, an application, or software whose presence is unknown or unwanted. Hard drives, which depend so heavily on mechanical components, are probably the most trouble-prone hardware components. CPUs, the true “brains” of computers, are surprisingly reliable. CPU problems can be hard to recognize.

Perhaps the biggest enemy of your computer’s CPU is heat. Modern processors generate a surprising amount of heat, and the failure to dissipate that heat effectively can lead to the processor’s slowing down or even to outright processor failure. Given that excess heat can be so damaging, it is surprising that more computers do not provide the ability to monitor processor temperature.

Several factors can cause heat problems. One of these is fan failure. Computers use fans in various configurations to move heat out of the computer’s case, and a non-functioning fan can cause the CPU to run hot. Sometimes, the first sign of trouble is that the computer has become quieter than usual, a common symptom of a fan that isn’t working.

Alas, symptoms of heat buildup are usually more subtle. A computer could be running slower than usual because the processor is too hot, but it could also be running slower because some application is misbehaving, because too much software is running at once, or because some piece of malware is sucking up all available CPU cycles. Software is the most common culprit when a computer is sluggish.

My own computer, i.e., the one I use most often, has been slow of late, and I suspected that software was indeed causing the problem. The CPU has often been running at or near 100% capacity, and I have been trying to understand why that should be so. Programs like Outlook and Firefox just seemed to be using more processing resources than they should. Yesterday, my computer began shutting itself down and, upon rebooting was telling me that overheating was the cause of the shutdown. Clearly, it was time to open the case and take a look at what was going on.

It took but a few minutes to discover the problem. My computer does not have a fan atop the CPU (or its heat sink), so that wasn’t the problem. The large fans that move heat through the case were running, so they weren’t the problem either. When I moved the green plastic duct that directs the output of one of the fans toward the CPU’s heat sink, I discovered that the heat sink was properly seated on the processor. (Heat sinks sometimes become dislodged, often during some maintenance operation.) What I did discover, however, is that I could not even see the fins of the heat sink; they were covered by a thick layer of dust. Clearly, the dust was blocking air flow across the fins and causing the CPU to overheat. I cleaned out the dust, and everything seems back to normal. As I write this, my CPU usage is running at about 30%, a dramatic reduction resulting from faster processing at a lower temperature.

Let this be a warning to you, particularly if your computer, like mine, sits on the floor. Computers that sit on the floor—and few “desktop” computers actually reside on desktops, it seems—do tend to pick up a lot of dust. I do open my computer’s case from time to time, and I do clean out some of the dust. The duct that directs air to the heat sink isn’t transparent, however—perhaps it should be—so the dust buildup on the heat sink was hidden from view, a problem I only now understand.

Do you know if there is sufficient air circulation through your CPU’s heat sink?

1 comment:

  1. This is a helpful post, Lionel. Thanks. My computer hasn't screeched to a stop yet, but it's running slowly. I haven't peeked inside for quite a while, so maybe I'd better take a look!


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