A reader recently sent in this letter:
Mr. Langa: A friend forwarded me your Year-End PC Tasks article, which was very interesting, except it doesn't apply to the millions (OK, maybe not that many) of us who have laptops.
My laptop frequently overheats, and besides buying a new machine, I have no idea what to do.... So what are the options?
You're certainly not alone, Samantha. When you include all the variants of portable PCs from slender, lightweight laptops up to full-sized "desktop replacement" notebooks, there are tens of millions of units in use. If you also include tiny, handheld PCs, the number goes even higher.
The problem in discussing notebooks and laptops is that portable PCs are much less standardized than are ordinary PCs, which enjoy a high degree of parts and technological uniformity from type to type and brand to brand. It's not just differences in shapes and sizes among portable PCs, but it's that different laptops/notebooks can employ different technologies, different ways to pack components inside the case, different power systems ....
Fortunately, Samantha's letter focuses on one particular issue--overheating--which is one area where a general discussion about laptops/notebooks actually can be quite useful.
You see, all "air-breathing" laptops/notebooks (those that rely on drawing air through the case for cooling) share at least a few similarities: There's usually one or more air intakes through which cool air enters the system; a heat exchanger that dumps excess thermal energy from the CPU or system as a whole into the incoming cool air; and one or more exhausts through which the now-warmed air exits the system, carrying the heat away.
Most higher-powered laptop/notebooks use one or more fans to assist the airflow; it's a miniaturized version of the same type of cooling system found in most full-sized PCs. But some laptop/notebook systems rely on natural convection--warm air rising--to move the air around. These systems still have case openings and an internal heat exchanger, but no fan.
Still other units, especially handhelds and some smaller, standard PCs, have no case openings for airflow. Instead, they use the case itself as a heat exchanger. These units tend to be lower-power to begin with, so they have less heat to dissipate. Overheating is a much rarer issue with these units; and any such problems are usually resolved simply by turning the unit off for a while, or moving it to a cooler spot (e.g., out of the sun).
For this article, we'll focus on the true "air breather" laptops/notebooks; those that have case openings, an internal heat exchanger and (usually) a fan. And, for convenience, we'll refer to this whole class of units as "laptops," even though some of them--"notebook" PCs, to the linguistic purists--are too large and heavy for routine laptop use. Similarly, we'll include "tablet" PCs in the general category of laptops; they fit into today's discussion as long as they have case openings for cooling.