ABHI Multi-Core Processors

8/3/2019 ABHI Multi-Core Processors

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MULTI-CORE PROCESSORTECHNOLOGY

Presented By:

ABHISHEK KUMAR SHRIVASTAVA

Computer Science and Engg.

(Final Yr.)


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Multi-core processors


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History

In the early 1970s the firstMicroprocessor was developed byIntel.

It was a 4 bit machine that wasnamed the 4004

The 4004 was followed by Intels8008 and 8080, as well as motorolas6800 and 68000


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Growth

With each new generation ofprocessors there were severaldevelopments such as:

Smaller size

Faster Increased heat dissipation

Greater Consumption of power


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Single Core Performance

One technique used to increase single core performance was:

Pipelining: starting other waiting instructions before thefirst finishes.


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Single Core continued

Another technique was multithreading

Multithreading involves execution of two separatethreads.

Time is divided and interlaced between the twothreads in order to simulate simultaneousexecution.


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Problems with Single Core

To execute the tasks faster you mustincrease the clock time.

Increasing clock time drasticallyincreases power consumption andheat dissipation to extremely highlevels, making the processorinefficient.


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Multi Core solution

Creating two cores or more on the same Dieincreases processing power while keepingclock speeds at an efficient level.

A processor with 2 cores running at efficientclock speeds can process instructions withsimilar speed to a single core processorrunning at twice the clock speed, yet thedual core processor would still consumeless energy.


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Multi-Core Advantages

While working with many threads, a Multi Coreprocessor with n cores can execute n threadssimultaneously by assigning a core to eachthread.

If it must process more than n threads , say x, itcan apply multithreading procedures with eachcore working with an average of x/n threads.

A Single core processor must multithread withevery single thread.


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Other Incentives

Improving an existing single core design or creatinga better one is problematic in the sense that it:

Is time consuming to design

Is risky to modify existing designs

Creating multi core processors is convenient in thesense that:

The name core 2 duo and similar names aregood for marketing.

It has lower manufacturing costs.

Uses proven processor designs.


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Implementations

Two main ways to have multiple cores interactare the shared memory model, and thedistributed memory model.

In the shared memory model,all cores share the same cache

memory.

In the distributed memory model,each core has its own cache

memory.


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Implementations continued

The Intel core duo design has aseparate L1 cache memory for eachcore, but both cores share an L2

cache.


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Implementations continued

The AMD Athlon 64 X2

implementation has

separate L1 and L2cache memory for each

core.


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Problems

Some of the current problems foundwith multi core processors include:

Memory/Cache coherence. As

mentioned earlier, someimplementations have distributed L1caches but must share an L2 cache.This poses the problem of makingsure each core keeps the otherupdated with changes in the data inits own cache.


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Problems continued

Multi threading is also a problemwhen the software being run is notdesigned to take advantage of the

multi core processor. This maymean that one core does most of thework which means that the processor

is running no more efficiently than asingle core.


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Future of Multi Core

Current debates focus over whetherfuture multi core processors shouldbe homogenous or heterogeneous.

That is, should all the cores be thesame or should there be a mix ofdifferent types?


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Future continued

Having all cores same makesproduction easier and keeps itscomplexity to a minimum.

However, having different cores thatare specialized in specific tasksincreases complexity but has thepotential to be much more efficientin speed and power consumption.


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References

http://www.intel.com/multi-core/

http://www.faqs.org/patents/app/20090055826

http://www.csa.com/discoveryguides

/multicore/review2.php?SID=s0s5lp3hcg6fa6pf2ba28u84d0


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