Presented ByManoj Prashanth Yuvaraj

Sanjana Rakhecha

IntroductionMulti core ProcessorIssuesCache CoherenceMulti ThreadingPerformancePower and TemperatureSolution

• Multi-core processors dominate computer's market.• A multi-core processor is a single computing component with two or more

independent actual processors, ]• Performance is always an issue when considering computers. • It is difficult to find a computer system which has high

performance and consumes low power. • When performance needs to be maximized,

power consumption will increase, which is not desirable.

• In 1965, Intel’s Gordon Moore predicted that the number of transistors on a chip would double every 12 months into the near future (he later refined this, in 1975, to every two years)

Save the room of motherboardFour single cores → In one die

We can use this room more efficiently◦ Simplicity

We need additional systems to control the several single cores.◦ Economical efficiency

A quad-core is much cheaper and efficient than two single cores

Closest to the processor is Level 1 (L1) cacheLevel 2 (L2) cache is just off-chipL2 cache is larger than L1 cache and used for the same purpose. Main memory is very large

Cooling, I/O, memory and cache.◦ clock speeds have declined: the more cores per processor

chip, the lower the clock frequency • Memory Bandwidth Bottleneck• Parallel programming, Speed leads to more power

consumption. • Multithreading.• Shared Caches.

Cache coherence is a concern in multicore processors because of distributed L1 and L2 cache.

Programmers have to write applications with subroutines able to be run in different coresIf one core is being used much more than another, the programmer is not taking full advantage of the multicore system.

Two cores on a single chip consumes twice as much power and generate a large amount of heat.This also creates hot spots. This requires cooling. The design runs the multiple cores at a lower frequency.

-Ex Intel Xeon Processor 5500 series. The designs incorporates a power control unit that shuts down unused cores or limit the amount of power. To lessen the heat generated, the chip is architected so that the number of hot spots doesn’t grow too large

Allows the processor to meet the instantaneous performance needs of operation.Clock speed of the processor is dynamically changed by software.Intel- Turbo Boost: processor to run above its base operating frequency via dynamic control of the CPU's "clock rate"AMD – Cool n Quiet : CPU speed throttling and power saving technology

Single job runtime, multi-job throughput, and parallel scalabilityPower scalingParallelism : Execution of many computing calculations carried out simultaneouslyCache coherence : A simple solution:invalidation-based protocol with snooping