Home' Technology Review : January February 2009 Contents FEATURE STORY
computing, that solution gives rise in turn to a tricky software
problem. How do you program for multiple processors? It's Anwar
Ghuloum's job to figure that out, with the help of programming
groups he manages in the United States and China.
Microprocessor companies take a huge risk in adopting the
multicore strategy. If they can't find easy ways to write software for
the new chips, they could lose the support of software developers.
This is why Sony's multicore PlayStation 3 game machine was late
to market and still has fewer game titles than its competitors.
THE PROBLEM WITH SILICON
For the first 30 years of microprocessor development, the way to
increase performance was to make chips that had smaller and
smaller features and ran at higher and higher clock speeds. The
original Apple II computer of 1977 used an eight-bit processor that
ran at one megahertz. The PC standard today is a 64-bit chip run-
ning at 3.6 gigahertz---e ectively, 28,800 times as fast. But that's
where this trajectory seems to end. By around 2002, the smallest
features that could be etched on a chip using photolithography
had shrunk to 90 nanometers---a scale at which unforeseen e ects
caused much of the electricity pumped into each chip to simply
leak out, making heat but doing no work at all. Meanwhile, transis-
tors were crammed so tightly on chips that the heat they generated
couldn't be absorbed and carried away. By the time clock speeds
reached five gigahertz, the chip makers realized, chips would get
so hot that without elaborate cooling systems, the silicon from
which they were made would melt. The industry needed a di er-
ent way to improve performance.
Because of the complex designs that high-speed single-core
chips now require, multiple cores can deliver the same amount
of processing power while consuming less electricity. Less elec-
tricity generates less heat. What's more, the use of multiple cores
spreads out whatever heat there is.
Most computer programs, however, weren't designed with mul-
tiple cores in mind. Their instructions are executed in a linear
sequence, with nothing happening in parallel. If your computer
seems to be doing more than one thing at a time, that's because the
When Anwar Ghuloum came to work at Intel in 2002,
the company was supreme among chip makers,
mainly because it was delivering processors that
ran at higher and higher speeds. "We were already
at three gigahertz with Pentium 4, and the road map called for
future clock speeds of 10 gigahertz and beyond," recalls Ghuloum,
who has a PhD from Carnegie Mellon and is now one of the com-
pany's principal engineers. In that same year, at Intel's developer
conference, chief technology o cer Pat Gelsinger said, "We're
on track, by 2010, for 30-gigahertz devices, 10 nanometers or less,
delivering a tera-instruction of performance." That's one trillion
computer instructions per second.
But Gelsinger was wrong. Intel and its competitors are still
making processors that top out at less than four gigahertz, and
something around five gigahertz has come to be seen, at least for
now, as the maximum feasible speed for silicon technology.
It's not as if Moore's Law---the idea that the number of transis-
tors on a chip doubles every two years---has been repealed. Rather,
unexpected problems with heat generation and power consump-
tion have put a practical limit on processors' clock speeds, or the
rate at which they can execute instructions. New technologies,
such as spintronics (which uses the spin direction of a single elec-
tron to encode data) and quantum (or tunneling) transistors, may
ultimately allow computers to run many times faster than they
do now, while using much less power. But those technologies are
at least a decade away from reaching the market, and they would
require the replacement of semiconductor manufacturing lines
that have cost many tens of billions of dollars to build.
So in order to make the most of the technologies at hand, chip
makers are taking a di erent approach. The additional transistors
predicted by Moore's Law are being used not to make individual
processors run faster but to increase the number of processors
inside a chip. Chips with two processors---or "cores"---are now the
desktop standard, and four-core chips are increasingly common.
In the long term, Intel envisions hundreds of cores per device.
But here's the thing: while the hardware problem of overheat-
ing chips lends itself nicely to the hardware solution of multicore
TO MOVE FORWARD, INTEL DUSTS OFF OLD
By ROBERT X. CRINGELY
Illustration by THE HEADS OF STATE
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