IEEE Spectrum April, 2012 - 13

smaller
traNsistors
Intel has packed 1.4 billion 3-D transistors onto
Ivy Bridge, its next-generation processor. The
switch to less leaky 3-D transistors has given the
new chip a big power boost. The 22-nm Ivy Bridge
chips can be run just as fast as the company's
previous chips, but with an operating voltage
that's 200 mV lower. Intel has also incorporated
designs at the circuit and core level to improve
the chip's power management. A separate
system-on-a-chip code-named Silvermont,
based on the same transistor-making process,
will be geared for mobile handsets.

all-digital
phase lockiNg

six paths to longer
Battery life
these six technologies could save
on smartphone power

he boom in mobile devices and data servers has
circuit designers racing to find new ways to slash
power consumption. At this year's International
Solid-State Circuits Conference, in San Francisco, six
power-saving technologies took center stage. Some will
emerge in products this year, while others are just beginning to catch the interest of major chipmakers.

Near-threshold
computiNg

leFt: Istockphoto; rIght: purdue unIversIty

Academics have long toyed with the idea
of operating chips at a point very close to
the threshold voltage-the amount needed
to switch a transistor on. Now the scheme
seems to be getting picked up by industry.
Intel researchers discussed a 32-nanometer,
Pentium-class chip they've built that
can operate from 1.2 volts-de rigueur for
today's processors-all the way down to
280 millivolts. The chip's sweet spot for
energy efficiency was 450 mV, just above the
threshold voltage. At that level, Intel's chip ran
slowly, at less than 100 megahertz, but it also
consumed just about a fifth of the energy it
did at 1.2 V. Parallel processing could be used
to pick up some of the slack in performance.
spectrum.ieee.org

razor-thiN margiNs
Engineers typically run chips at a higher
voltage than needed in order to prevent
clocking errors. If chips had a way to detect
errors and change their operating voltage
on the fly, engineers could push chips to
operate at the lowest voltage possible,
saving power in the process. The scheme,
called Razor, is still largely stuck in
academic circles. But researchers from
the University of Michigan, in Ann Arbor,
and Harvey Mudd College, in Claremont,
Calif., showed that the approach works
on an ARM Cortex-M3 processor, boosting
energy efficiency by 60 percent. The
team says it's the first implementation
of a Razor-style scheme on a complete
commercial processor.

Phase-locked loops-which lock in and track
an input signal-are vital circuit elements that
are used to sync modern processors to their
clocks and pick up and transmit radio signals.
In the past, these circuits were built with
analog components, but all-digital variants
consume a tenth of the power and are easier
to fabricate. Mobile powerhouse Samsung
presented a new improvement on the alldigital phase-locked loop, a 0.012-squaremillimeter circuit that consumes just 2.5 mW.
Intel showed off a version of the circuit, built
with the company's 22-nm technology, that
consumes as little as 0.7 mW.

smart coNverters
Another basic circuit headed for a low-power
makeover is the switched capacitor, which
is often used to convert analog signals to
digital. A team at Oregon State University,
in Corvallis, debuted a low-power component
that was inspired by the ring oscillator,
a common test circuit made of a loop of
inverters. Another team at the National
Chiao Tung University, in Hsinchu, Taiwan,
found a way to save power by working on
signals in two separate stages-one for crude
processing and the other for fine-tuning-
that can each be optimized.

Next-geNeratioN
dyNamic ram

news
brief
A SingleAtom
Transistor
Researchers in
Australia, South
Korea, and the
United States
have created
a working
transistor out
of a single
phosphorus
atom embedded
in silicon. They
used a scanning
tunneling
microscope and
a technique
common in
lithography to
replace one
silicon atom
in a six-atom
lattice with a
phosphorus
atom. When
they applied a
voltage across
the phosphorus
atom, it behaved
like a transistor,
switching and
amplifying an
electric current.

Memory makers Samsung and Hynix
Semiconductor both unveiled details
on the next incarnation of synchronous
DRAM, the memory that drives today's
processors. The new generation, which goes
by the name DDR4, boasts circuit tricks that let
Samsung drop the supply voltage to its memory
modules from 1.5 V to 1.2 V. The modules also
include better clocking and faster algorithms
for encoding data to be sent to and fetched
from memory. DDR4 may make its commercial
debut as early as 2013.
-Rachel Courtland
april 2012 * iEEE SpEctrum * Na

http://spectrum.ieee.org

Table of Contents for the Digital Edition of IEEE Spectrum April, 2012