14 March 2020 | New Scientist | 41
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two remarkable trends working in tandem.
The first was industry’s ability to miniaturise
transistors and double the number of them
that could be squeezed on a computer chip
roughly every two years, a trend referred to
as Moore’s law. The second was an observation
from computer scientist Robert H. Dennard
that the power consumption of individual
transistors fell in proportion to their reduced
size. This meant you could double a chip’s
computing power at the same time as its
energy efficiency.
Breaking Moore’s law
However, these advances couldn’t last forever.
Roughly 15 years ago, silicon transistors started
getting so small that further efficiency gains
became physically impossible. Today, the
number of transistors per chip continues
to rise, but packing them closer together is
getting increasingly complicated. This is
because the extra heat given off causes chips
to malfunction. “We really are hitting a wall
in terms of designing these at smaller and
smaller dimensions,” says Iris Bahar at Brown
University in Rhode Island. “We are getting
close to the limit of how efficient they can be.”
For the first time in 50 years, Moore’s law is
beginning to falter (see “Power slump”, page 43).
At the same time, demand for ever smaller,
ever more powerful computers is booming.
Upgrading mobile data networks from 4G to
5G technology, which will make download
speeds up to 100 times faster, is expected to see
average monthly data use in North America
balloon from 8.6 gigabytes per person in 2019
to 50 gigabytes in 2024. There has also been
an explosion in web-connected devices,
175 zettabytes
the total amount of data forecast
to exist by 2025
6 per cent
the share of the world’s electricity
currently devoted to computing
