Some thoughts about Moore’s law & technology trends

Sameh Galal

9/24/2009

Why this presentation?

• Everybody loves to talk about Moore’s law starting from process engineers all the way to singularity futurists.

• However this talk is different, as it does not have an extremely gloomy vision of post moore’s law world.

• It is more about connecting different news, data points, and try to construct a context for them. i.e. trying to understand the world.

• This presentation will be more handwavy than scientific (more Michael Moore style than a Gordon Moore’s one)!!

Original Moore’s law (1965)

Dennard Technology Scaling (1972)

FIGURE 1.16 Growth in processor performance since the mid-1980s. This chart plots performance relative to the VAX 11/780 as measured by the SPECint benchmarks (see Section 1.8). Prior to the mid-1980s, processor performance growth was largely technologydriven and averaged about 25% per year. The increase in growth to about 52% since then is attributable to more advanced architectural and organizational ideas. By 2002, this growth led to a difference in performance of about a factor of seven. Performance for fl oating-pointoriented calculations has increased even faster. Since 2002, the limits of power, available instruction-level parallelism, and long memory latency have slowed uniprocessor performance recently, to about 20% per year. Copyright © 2009 Elsevier, Inc. All rights reserved.

Turbocharged Scaling (Double up)

With the cost of …

And then the hangover

• First, Power density hit the roof

– Stopped the turbo charging and went back to dennard scaling to keep power density constant around 100 W/cm2

• Then, Even Dennard scaling was not possible since Voltage scaling has slowed down as well, which means increased power density if frequency is increased. i.e. frequency scaling stopped as well.

Solution: give most of the chip to low power density parts

Solutions for single threaded performance

• Make huge caches! It improves both performance and power efficiency– 8-12 MB L3 caches in

current high end processors

• Nehalem Intel® Turbo Boost Technology: just yesterday, a laptop turbo chip (Core i7 mobile) was introduced by intel.

If you can’t improve performance…

• Then we can change what performance means!

• Now we say we are open to parallelism, and performance is the amount of computation we get per a certain area and power budget. (i.e. the Watt/Gflop and mm2/Gflop we get for a certain power density Watt/mm2 )

• Now dennart scaling improves our newly defined performance by 8X for halfing the feature size vsthe 2X improvement in single threaded performance

That has worked well so far

But diminishing returns are catching up again

• For throughput performance, dennart scaling would have given 8X improvement for halfing the feature size with a 2X improvement in single threaded performance

• Because of slowing of voltage scaling we get around 4X improvement now and we can get another 1.5-2X from moving to lower energy architectures and no improvement in single threaded performance

• In the future we will get only 2X improvement when voltage scaling stops completely and we have to have degraded single threaded performance

From 90 nm to 45 nm is still ok.

Figure 7. Scaling of FMA single and double precision designs from 90nm to

45nm. The performance gain depends on the power density allowed.

And future is worse: only 2X factor and slower individual cores

Undoing the last 20 years of Computer Architecture Tricks

The world has changed as well

“Traditionally, PC makers relied on their software partners to build bulkier, more demanding applications that required new hardware. But that strategy has fallen apart. Consumers and businesses balked at Microsoft’s bloated Vista operating system, so the company’s upcoming Windows 7 software should actually require less horsepower and storage space to run well. The same goes for Apple’s new Snow Leopard operating system.”

* New York Times, Sep 11, 2009 “Goodbye, Gobbledygook: PC Makers

Abandoning a Sales Pitch Built on Complex Specs”

Software people lukewarm reception of parallelism

“…. I might as well flame a bit about my personal unhappiness with the current trend toward multicore architecture. To me, it looks more or less like the hardware designers have run out of ideas, and that they’re trying to pass the blame for the future demise of Moore’s Law to the software writers by giving us machines that work faster only on a few key benchmarks! I won’t be surprised at all if the whole multithreading idea turns out to be a flop, worse than the “Itanium" approach that was supposed to be so terrific—until it turned out that the wished-for compilers were basically impossible to write.

Let me put it this way: During the past 50 years, I’ve written well over a thousand programs, many of which have substantial size. I can’t think of even five of those programs that would have been enhanced noticeably by parallelism or multithreading. Surely, for example, multiple processors are no help to TeX.”

Dan E. Knuth, Stanford Professor Emeritus, author of The Art of Computer Programming and inventor of the TeX computer typesetting system in interview in 2008

And the money is not growing fast to support the more expensive scaling

The missing drivers

• Single threaded performance– At a certain point, a 128 MB cache becomes ridiculous

– As more people get used to stagnating performance, the people who need performance will move to parallelism

• Throughput performance– However, a lackluster 2X improvement for halfing the feature size instead

of 8X so far. Worse still, newer machines have to run slower than old ones.

• Market drivers– Lack of a killer application and people don’t care. The best sold PCs are

now netbooks

– Software does not push hardware anymore. Think Windows 7 and snow leopard as leading the software move of the future.

So what is next?

• Traditionally, the end of Moore’s law has always been 15 years in the future

• However, this time, we have very high cost of bridging the frontiers and not matching high returns or high market demand.

• I would argue that Moore’s law would not be undone by technical obstacles but rather its irrelevance. The day we don’t notice the noticeable difference Moore’s law exerts on our lives is when it will either dramatically slow down or stop.

• Of course never underestimate the probability of happy surprises

So how does the future of Computing without Moore’s law look like?

In 1927, GM president Alfred Sloan founded the “Art and Color Section” – the first design department ever set up by a car manufacturer. GM also had much success with its strategy of “a car for every purse and purpose”

Without moore’s law, we are all mechanical engineers.

• Design oriented vs Engineering oriented: people buy cars based on emotional attachment. Same is happening now with computers. Think Apple.

• Chip manufacturing the Toyota way: check out the IEEE spectrum article from May 2008 on “the new economics of Semiconductor Manufacturing”

If you ask the “all-knowing” prescient market, Moore’s law has stopped already

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