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The problem is, as PC Pro's own David Fearon noted (see issue 147, p13), this covers only the energy during use, ignoring that consumed during the processor's manufacture, distribution and eventual recycling. Since the United Nations University estimates that 80% of the energy used in a processor's lifetime is consumed during manufacture, this isn't a minor omission.

Second, VIA's "treemark" is calculated using some hefty assumptions. While VIA's maths assumes 24/7 operation over three years,

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it also assumes that 27% of that time will be spent in standby mode, 3% in sleep mode, 67% in idle mode and only 3% in performance mode. Use the processor for four years, or spend more time in power-hungry applications, and your CPU won't be carbon-free.

Similar questions dog VIA enthusiast Tranquil PC. This company is about as environmentally friendly as PC manufacturers come - it offsets the carbon cost of the system as a whole against trees planted in Kenya, then does the same for its own manufacturing operations. What's more, by using low-power components, it claims that buying a Tranquil PC instead of another brand can save you approximately £26.40 off your annual electricity bill. This time, however, the calculations assume your system will only be used eight hours a day, with only two hours of heavy workload, and will remain unplugged over weekends. This may be realistic for a business system, and the hours would probably balance out with a home PC, but if you work longer hours or keep the system for longer than the assumed three years, goodbye carbon-free computing.