2. Introduction:
What is Processor?
• A processor is the logic circuitry that responds to and
processes the basic instructions that drive a computer.
The term processor has generally replaced the term
central processing unit (CPU). The processor in a
personal computer or embedded in small devices is
often called a microprocessor .
3. What Is Core?
• Actually, a CORE is the part of something that is central
to its existence or character.
• Similarly, in computer system the CPU is referred as
CORE.
• Basically, there are two types of core processor:
1. Single Core Processor
2. Multi Core Processor
4. Single Core processor
It is a processor that has only one core, so it can only start
one operation at a time. It can however in some situations
start a new operation before the previous one is complete.
Originally all processors were single core. Examples are
Intel Pentium 4 670, AMD Athlon 64 FX-55.
5. Multi Core Processor
• A multi-core processor is one which combines two or
more independent processors into a single package,
often a single integrated circuit. Examples are Intel core
i7, intel core 2 duo.
6. Processor consists:
• A single chip package that fits in a socket
• Cores can have functional units, cache, etc.
associated with them, just as today
• Cores can be fast or slow, just as today
• Shared resources
• More cache
• Other integration: Northbridge, memory controllers, high-
speed serial links, etc.
• One system interface for System Bus and System Memory
7. Problems with Single Core
a. To execute the tasks faster you must increase the clock
time.
b. Increasing clock times too high drastically increases
power consumption and heat dissipation to extremely
high levels, making the processor inefficient
8. Multi Core solution
A. Creating two cores or more on the same Die increases
processing power while keeping clock speeds at an
efficient level.
B. A processor with 2 cores running at efficient clock
speeds can process instructions with similar speed to a
single core processor running at twice the clock speed,
yet the dual core processor would still consume less
energy.
9. Why Multi-core?
– Better Performance
– For the Multi tasking
– e.g. Burning CD with graphic works at the same
time
– Power consumption and Heat generation Caused
from the advance of CPU clock speed
10. Why Multi-core?
• Save the room of motherboard
• Two 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 dual-core is much cheaper than two single
cores
11. If multi means two or more, what types
are there?
A dual-core processor A quad-core processor
contains two cores contains four cores
13. Shared caches
• As the trend moves from single-core to multi-core
processors for the next computing performance leap,
system architectures have several options for the
organization of one of the most important system
resources-the cache. Some architectures choose to
keep the last-level cache private to each core for
simplicity, while other architectures explore sharing the
last-level cache among different cores for better
performance/cost ratio and improved resource allocation.
14. Benefits of the shared cache architecture
• Figure 1 shows two processors (processor 0 and
processor 1) sharing the same system bus and system
memory. Inside each processor there are two CPU
cores; each has its own private L1 cache while sharing
the L2 cache. The benefits of such a shared cache
system are many:
15. Benefits of the shared cache architecture
• Efficient usage of the last-level cache If one core idles,
the other core takes all the shared cache
• Reduces resource underutilization
• Flexibility for programmers Allows more data-sharing
opportunities for threads running on separate cores that
are sharing cache
• One core can pre-/post-process data for the other core
• Alternative communication mechanisms between cores
16. Benefits of the shared cache architecture
(cont)
• Reduce cache-coherency complexity Reduced false
sharing because of the shared cache
• Less workload to maintain coherency, compared to the
private cache architecture
• Reduce data-storage redundancy The same data only
needs to be stored once
17. Benefits of the shared cache architecture
(cont)
• Reduce front-side bus traffic Effective data sharing betw
een cores allows data requests to be resolved at the
shared-cache level instead of going all the way to the
system memory
19. Cache coherence
• “For any given memory location, at any given
(logical) time, there is either a single core that may
write it (and that may also read it) or some number
of cores that may read it.”
Cache coherence: definition
Two fundamental invariants:
● Single-Writer-Multiple-Reader (SWMR)
● Data-Value
20. Cache Consistency
• A specification of the allowed behavior of
multithreaded programs executing with shared
memory
● Multiple correct behaviors are usually allowed
One fundamental:
● Out-of-Order execution
21. Performance Enhancement
• Pipelining concept used i.e. subsequent instruction
begins to execute before completion of the previous one
or allowing parallel processing.
22. Performance Enhancement Contd.
• Multithreading i.e. time is divided and
interlaced between more than one thread
to simulate simultaneous execution.
23. Applications of Multicore
• 3D Gaming
• Database servers
• Multimedia applications
• Video editing
• Powerful graphics solution
• Encoding
• Computer Aided Design (CAD)
24. Advantages
• Signals between different CPUs travel shorter distances,
those signals degrade less.
• These higher quality signals allow more data to be sent
in a given time period since individual signals can be
shorter and do not need to be repeated as often.
• A dual-core processor uses slightly less power than two
coupled single-core processors.
• More features can be added to the computer
25. Disadvantages
•They do not work at twice the speed as a normal
processor. They get only 60-80% more speed.
•The speed that the computer works at depends on what
the user is doing with it.
•They cost more than single core processors.
•They are more difficult to manage thermally than lower-
density single-core processors.
26. EXAMPLES
dual-core processor with 2 cores
e.g. AMD Phenom II X2, Intel Core 2 Duo E8500
quad-core processor with 4 cores
e.g. AMD Phenom II X4, Intel Core i5 2500T)
hexa-core processor with 6 cores
e.g. AMD Phenom II X6, Intel Core i7 Extreme Ed. 980X
octa-core processor with 8 cores
e.g. AMD FX-8150, Intel Xeon E7-2820
