tal physical obstacle than any in its
history. ‘As we make smaller and smaller
circuits that are more and more densely
packed, the number of atoms that you use
per component is being reduced. As you
go down there is a fundamental physical
process which changes: your circuits are
not deterministic any more, they are
probabilistic. They become random, and
as they become random they become less
reliable.’
Gelenbe believes this atomic hurdle is
already beginning to impact on the
semiconductor industry’s roadmap. ‘If
you look at the industry conference
themes, there’s been a shift toward
probabilistic circuits.
‘The question is, despite the fact that
these individual circuits are less
predictable, can we still build systems
that are predictable and reliable using
them?’
And according to Gelenbe, there is at
least one good piece of existing evidence
that probabilistic computing works and
works well: the human brain.
‘You and I are highly unreliable
organisms, our brains make mistakes but
we get most of it right — just think of the
amount of computing we do as we walk
down the street and we do it reliably,
despite the fact that all of our underlying
mechanisms are unreliable.’
Intel’s Knupffer agrees with Gelenbe’s
analysis, but declined to make a
Moore-style prediction about what the
future might hold.
‘We are reaching the limits of the
CMOS [complementary metal–oxide–
semiconductor] process. We haven’t
announced anything beyond 11nm —
future options could include spintronics
(a technique that exploits the spin of
electrons), optical or photonic computing,
or quantum computing. Work is ongoing
in all these areas, it could be none of them
or it could be all of them. The one thing
we are saying is that we intend to use
silicon as a building block.’
And though the challenges facing the
semiconductor industry are huge, its
optimism in a future that it admits it
cannot predict might just keep Moore’s
Law afloat. Knuppfer said: ‘Every
time we build a fab, it’s a $3bn or $4bn
investment. We’re taking a giant step,
because we’re building a fab that will
create processors that haven’t been
designed yet on a process that hasn’t been
invented yet for a market that doesn’t
exist yet.
‘It’s a pretty big bet.’
the EnGIneeR 15–28 SEPTEMBER 2008
Intel’s silicon
modulator under
test, right, and in
close up, centre
right. Bottom
right, the
company’s single
modulator chip
SEMICONDUCTOR TECHNOLOGY
25
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