As soon as you back off, say by switching off the background music and allowing your foreground process to have all the processing power (and thereby complete its task more quickly), the benefits of having a dual-core machine will become far less tangible.

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Especially confusing, says Gazzaley, is that key brain functions, like short-term memory, processing speed, and the capacity to multi-task, decline steadily as we age.

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If you are looking to get one task done fast, you need to deploy parallel processing.

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Technological changes such as the rise of collaboration tools make it easier to multi-task: you can have a chat window, a word-processing document, a Web browser, and other applications all open at the same time on your computer, and switch easily between them.

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The idea is to couple the central processing units (CPUs) cranked out by Intel and AMD, which can move nimbly from one kind of task to another, with the GPUs put out by AMD and Nvidia, which are good at grinding through vast numbers of tasks at the same time.

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