The decades-old approach of powerful processors with ever-faster
clock speeds is changing. Performance matters in some settings, but
the real concern is adding more functionality within power budgets.
The most pressing tradeoff is now performance vs. power, which has
forced processor architects at AMD, Intel and IBM to take into
account everything from application software to the firmware that
manages some of the functions on a chip and the middleware that
makes it all work together.
“One phenomenon we’re seeing is that a number of customers claim
their data centers are full but when we go out to see them they’re
only half full of hardware,” said Margaret Lewis, product marketing
director at AMD, “They can’t draw any more power in places like the
Northeastern United States, California or Germany.”
Part of that is due to virtualization, which has been pushed on
data centers in particular as the way to boost utilization of a
server. According to McKinsey & Co., datacenter server
utilization is as low as 5%, which has made virtualization a
natural way to improve efficiency and cut costs. And with many
software applications unable to utilize more than a couple cores of
a server, it’s sometimes only way to boost utilization of multicore
servers.
That is about to change, however. “Most of the software hasn’t made
it over to multithreading,” Lewis said. “So instead of just using
cores for applications, there are other switches we can turn on
processors to do things like balance memory or have better I/O.”
The software also can be tweaked to boost optimization lower down
on the stack so that instead of tuning each Java virtual machine
running on a separate core they all can be optimized so that every
Java applet benefits.
“We are seeing a number of new software models,” Lewis said. “The
only thing that keeps everything around is that the legacy software
people don’t want to give up what they have. It’s easy to
multithread to two to four cores. After that, debugging becomes too
difficult. A different approach is multitasking, so you do
different tasks on different cores. What’s being done with the CPU
and the GPU is the first big example of that.”
Intel, meanwhile, has been working with Microsoft to improve the
efficiency of its processors.
“Performance was always the focus, but power savings are now part
of the methodology,” said George Alfs, program manager at Intel.
“For years we have been working with Microsoft to make sure that
the operating system isn’t spinning wildly waiting for the next
keystroke. We’re now putting the operating system into a sleep
state even between keystrokes. There are seven sleep states and a
variety of ways to take advantage of power.”
Part of Intel’s road map also calls for more threading. Windows 7
is expected to offer better scheduling than Vista, allowing more
than one application to run at the same time on different cores. It
also calls for power flexibility to provide more thermal headroom
for either boosting performance or lowering power at 32nm.
Intel also is building basic graphics processing into the
processor, which will further utilize some of the cores. How many
cores depends on the graphics requirements. The first Larrabee
chip, due out next year, has a discrete graphics card for ray
tracing, but there is certainly a possibility that Intel could
integrate some of those graphics into its processors.
Intel also will be using a combination of homogeneous and
heterogeneous cores, Alfs said, which is a different direction than
the company said it would take several years ago. Some of those
cores could be for I/O and graphics, Alfs said, similar to the
approach taken by AMD. Intel also plans to use some cores for
encryption/decryption, which has been a drag on system performance
in the past.
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