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To: hlpinout who wrote (89562)2/7/2001 7:43:34 PM
From: hlpinout  Read Replies (1) | Respond to of 97611
 
From The Register.

--
Intel touts Alpha, IBM designs to beat 'hotter
than reactor'chips
By: Andrew Orlowski in San Francisco
Posted: 06/02/2001 at 00:44 GMT

Chips will be as hot as nuclear reactors by the end of the decade... and
as hot as the surface of the sun by 2015, if they continue on their current
design path, according to Pat Gelsinger, Intel's architecture chief.

Obviously something's got to give if these thermal problems can't be
solved: which he characterises as "no longer business as usual".

Interestingly, two of his suggested remedies for beating the heat and
power consumption issues are borrowed from Chipzilla's competitors.
These are: SMT which will be used in future revs of Alpha processor;
and the multiple cores on a die approach adopted by IBM for POWER4
and Sun Microsystems for its MAJC processor. The former may already
supported, according to some reports, in Intel's Foster chip: it's Pentium
4 for servers. And diligent Reg readers have pointed out that we first
discussed this here.

Kicking Pat delivered the keynote at the IEEE's International Solid State
Circuits conference, which draws over 3,000 semiconducor engineers to
San Francisco.

The nub of his presentation is this. Moore's law will remain true for the
next ten years: but the thermal properties and power requirements of
future chips conforming Moore's rule of thumb will be unsellable, unless
design approaches are radically revised.

"No one," as Gelsinger puts it,"wants to carry a nuclear reactor in their
laptop onto a plane". He acknowledges that Intel has contributed to the
general power and thermal issues by sacrificing efficiency for
performance in the push for higher frequencies, by designing deeper
pipelines, with less gates per pipeline. "We make big fat transistors to
drive up the frequency."

"I don't think these decision were bad... but I don't think we know to cool a
5000W chip." Keeping the die size constant, or maintaining voltage as a
constant for future generations of chips are inadequate answers, he
says.

Engineers woll have to design their way past thermal issues. Heat isn't
the only issue: memory latencies are bad, and getting worse, with 1000
clock cycle penalty for going out to main memory after a cache miss "a
truly whopping number," according to Gelsinger, momentarily slipping
into Reg-Speak. "It's a fairly dire picture."

Rotten to the Core
There are of course a host of new design approaches the industry can
take. Gelsinger says Intel has been checking out multi-threading
processors that look like two or more CPUs to software applications.

Compaq calls this SMT, or simultaneous multi-threading, and it will
appear in EV8 Alphas next year. With SMT, the software sees a 4way
SMP box; and it will supersede earlier Alphas for Compaq's VMS and
Tru64 lines, and replace the MIPS processors used in its Himalaya
servers today.

Such a model adds maybe 10 per cent to the logic on a chip, but adds
under 10 per cemt thermal cost, compared to a 2x increase in heat and
power for conventional revs, according to Intel estimates cited by
Gelsinger. It also provides a cheap SMP. But the problem is, he says, is
that few applications use pervasive multithreading (BeOS users will
disagree, but alas, there aren't really that many of us).

The multiple cores on a die approach of MAJC and POWER4 also
offered benefits, he says. Like SMT, it allowa the chip to throttle back
performance, rather than design around worst-case, flat out,
all-pipelines-full scenarios, which hardly ever happen. Fancy that, we
thought.

Other approaches are to offload specific computational tasks onto a
dedicated integrated DSP or special instruction set, such as SSE2.

Alphabet Soup
But some questions remain. Is Foster's Jackson Technology really SMT,
or an aid to help SMP threads?

If it's SMT, then what will the Alpha design team over in Massachusetts
make of Intel's Damascene conversion? Of course, when the Great
Satan of Walk-In Wardrobes settled DEC's Alpha-Pentium lawsuit,
Palmer worked out some pretty complex intellectual property sharing and
manufacturing agreements with Grove.

Does this now allow Intel first dibs on SMT? And if so, what's in it for Big
Q? ®