The Quest for More Processing Power, Part One: "Is the single core CPU doomed?"
by Johan De Gelas on February 8, 2005 4:00 PM EST- Posted in
- CPUs
Conclusion
Prescott was built to adapt to the typical problems that made it hard to run x86 programs quickly: branches, dependencies, lots of memory and ADD operations. However, in order to do so, complex logic was used, which increased leakage power quickly. The wire delay problem and dependency problem were only solved by sacrificing a lot of energy. The combination of LVS double-pumped ALUs, tons of new features and 64 bit together created an avalanche of leaking logic. The result is an innovative architecture crushed into a thermal wall.
But the Prescott failure, the exploding leakage power and wire delay don't mean automatically that the single core CPUs have no future. Power leakage can be contained by introducing high-K materials and SOI. Wire delay has been solved by using repeaters - at the cost of some extra power - and Cu interconnects. Dual core is not a magical solution that is going to solve all the problems that Prescott and other modern CPU face.
The Prescott failure only tells us that right now, the ultra deep pipelined CPU is not the best solution. Intel went too quickly, too deep, and although many ingenious tricks were implemented to make the Prescott a real powerhouse, all those tricks together backfired with high leakage and dynamic power loss.
In the next article, we investigate what dual core technology can really bring us, besides a lot of hype, "paradigm shift" slogans everywhere and "much smoother system" claims.
References
[1] An In-Depth Look at Computer Performance Growth
CHALMERS UNIVERSITY OF TECHNOLOGY, Department of Computer Engineering, Göteborg 2004
http://www.ce.chalmers.se/~warg/papers/performancegrowth_tr-2004-9.pdf
[2] Intel Whitefield uncovered, The Register
http://www.theregister.co.uk/2004/05/01/intel_whitefield_uncovered/
[3] Implementing Power Management IP forDynamic and Static Power Reduction in Configurable Microprocessors using the Galaxy Design Platform at 130nm
Dan Hillman, Virtual Silicon
John Wei, Tensilica
http://www.tensilica.com/hillman_slides.pdf
[4] Leakage Power Modelling and Leakage Power Modelling and Minimization
Massoud Pedram
University of Southern California , Dept. of EE-Systems
http://atrak.usc.edu/~massoud/Papers/pedram-tutorial-iccad04.pdf
[5] Gigascale Integration-Challenges and Opportunities
By Shekhar Borkar
Intel Fellow, Director, Circuit Research
http://www.intel.com/research/mrl/research/circuit.htm
http://www.intel.com/cd/ids/developer/asmo-na/eng/strategy/182440.htm?page=1
[6] SUN Niagra Demo
http://www.sun.com/aboutsun/media/presskits/networkcomputing05q1/
[7] LVS Technology for the Intel® Pentium® 4 Processor on 90nm Technology
http://www.intel.com/technology/itj/2004/volume08issue01/art04_lvs_technology/p01_abstract.htm
Other Sources:
- Intel Silicon Innovation To Shape Direction Of The Digital World
Multi-Core Processors, FALL IDF 2004
http://www.intel.com/pressroom/archive/releases/20040907corp.htm - Pentium 4 processor at 4.7 GHz, FALL IDF 2002
http://www.intel.com/pressroom/archive/releases/20020909corp.htm - Intel Developer Forum, Spring 2002
Louis Burns Keynote, Netburst architecture scales up to 10 GHz.
http://www.intel.com/pressroom/archive/speeches/burns20020227.htm - The Free Lunch Is Over: A Fundamental Turn Toward Concurrency in Software
By Herb Sutter
http://www.gotw.ca/publications/concurrency-ddj.htm - Illinois researchers create world's fastest transistor ... again
http://www.news.uiuc.edu/scitips/03/1106feng.html
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stephenbrooks - Wednesday, February 9, 2005 - link
#28 - that's interesting. I was thinking myself just a few days ago "I wonder if those wires go the long way on a rectangular grid or do they go diagonally?" Looks like there's still room for improvement.Chuckles - Wednesday, February 9, 2005 - link
The word comes from Latin. "mono" meaning one, "lithic" meaning stone. So monolithic refers to the fact that it is a single cohesive unit.The reason you associate "lithic" with old is only due to the fact that anthropologists use Paleolithic and Neolithic to describe time periods in human history in the Stone Age. The words translate as "old stone" and "new stone" respectively.
I have seen plenty of monolithic benches around here. Heck, a slab granite countertop qualifies as a monolith.
theOracle - Wednesday, February 9, 2005 - link
Very good article - looks like a university paper with all the references etc! Looking forward to part two.Re "monolithic", granted the word doesn't mean old but anything '-lithic' instantly makes me think ancient (think neolithic etc). -lithic means a period in stone use by humans, and a monolith is a (usually ancient) stone monument; I think its fair to say Intel were trying to make the audience think 'old technology'.
DavidMcCraw - Wednesday, February 9, 2005 - link
Great article, but this isn't accurate:"Note the word "monolithic", a word with a rather pejorative meaning, which insinuates that the current single core CPUs are based on old technology."
Neither the dictionary nor technical meanings of monolithic imply 'old technology'. Rather, it simply refers to the fact that the single-core CPU being referred to is as large as the two smaller chips, but is in one part.
In the context of OS kernel architectures, the Linux kernel is a good example of monolithic technology... but I doubt many people consider it old tech!
IceWindius - Wednesday, February 9, 2005 - link
Even this articles makes my head hurt, so much about CPU's is hard to understand and grasp. I wish I kneow how those CPU engineers do this for a living.I wish someone like Arstechinca would make something really built ground up like CPU's for morons so I could start understanding this stuff better.
JohanAnandtech - Wednesday, February 9, 2005 - link
Jason and Anand have promised me (building some pressure ;-) a threaded comment system so I can answer more personally. Until then:1. Thanks for all the encouraging comments. It really gives a warm feeling to read them, and it is basically the most important motivation for writing more
2. Slashbin (27): Typo. just typed with a small period of insanity. Voltage of course, fixed
3. CSMR: the SPEC numbers of intel are artificially high, as they have been spending more and more time on aggressive compiler optimisations. All other benchmarks clearly show the slowdown.
CSMR - Tuesday, February 8, 2005 - link
Excellent article. Couple of odd things you might want to amend in chapter one: "CPUs run 40 to 60% faster each year" contradicts the previous discussion about slowed CPU speed increases. Also power formula explanation on the same page doesn't really make sense as pointed out by #27.Doormat - Tuesday, February 8, 2005 - link
Good article. The only real thing I wanted to bring up was something called the "X Consortium". I wrote a paper in my solid state circuit design class a few years ago. Basically instead of having all the interconnects within a chip laid out in a grid-like fashion, it allows them to be diagonal (and thus, a savings of, at most, 29% - for the math impaired it could be at most 1/sqrt(2)). Perhaps the tools arent there or its too patent encumbered. If interconnects are really an issue then they should move to this diagonal interconnect technology. I actually dont think they are a very pressing need right now - leakage current is the most pressing issue. The move to copper interconnects a while ago helped (increased conductivity over aluminum, smaller die sizes mean shorter distances to traverse, typically).It will be very interesting to see what IBM does with their Cell chips and SOI (and what clock speed AMD releases their next A64/Opteron chips at since they've teamed with IBM). If indeed these cell chips run at 4GHz and dont have leakage current issues then there is a good chance that issue is mostly remedied (for now at least).
slashbinslashbash - Tuesday, February 8, 2005 - link
" In other words, dissipated power is linear with the e ffective capacitance, activity and frequency. Power increases quadratically with frequency or clock speed." (Page 2)Typo there? Frequency can't be both linear and quadratic..... from the equation itself, it looks like voltage is quadratic. (assuming the V is voltage)
AnnoyedGrunt - Tuesday, February 8, 2005 - link
And of course I meant to refer to post 23 above.-D!