computer science crazy
Guest
Definition
Seeing the technical difficulties in cranking higher clock speed out of the present single core processors, dual core architecture has started to establish itself as the answer to the development of future processors. With the release of AMD dual core opteron and Intel Pentium Extreme edition 840, the month of April 2005 officially marks the beginning of dual core endeavors for both companies.
The transition from a single core to dual core architecture was triggered by a couple of factors. According to Moore's Law, the number of transistors (complexity) on a microprocessor doubles approximately every 18 months. The latest 2 MB Prescott core possesses more than 160 million transistors; breaking the 200 million mark is just a matter of time. Transistor count is one of the reasons that drive the industry toward the dual core architecture. Instead of using the available astronomically high transistor counts to design a new, more complex single core processor that would offer higher performance than the present offerings, chip makers have decided to put these transistors to use in producing two identical yet independent cores and combining them in to a single package.
To them, this is actually a far better use of the available transistors, and in return should give the consumers more value for their money. Besides, with the single core's thermal envelope being pushed to its limit and severe current leakage issues that have hit the silicon manufacturing industry ever since the transition to 90 nm chip fabrication, it's extremely difficult for chip makers (particulary Intel) to squeeze more clock speed out of the present single core design. Pushing for higher clock speeds is not a feasible option at present because of transistor current leakage. And adding more features into the core will increase the complexity of the design and make it harder to manage. These are the factors that have made the dual core option the more viable alternative in making full use of the amount of transistors available.
What is a dual core processor?
A dual core processor is a CPU with two separate cores on the same die, each with its own cache. It's the equivalent of getting two microprocessors in one. In a single-core or traditional processor the CPU is fed strings of instructions it must order, execute, then selectively store in its cache for quick retrieval. When data outside the cache is required, it is retrieved through the system bus from random access memory (RAM) or from storage devices. Accessing these slows down performance to the maximum speed the bus, RAM or storage device will allow, which is far slower than the speed of the CPU. The situation is compounded when multi-tasking. In this case the processor must switch back and forth between two or more sets of data streams and programs. CPU resources are depleted and performance suffers.
In a dual core processor each core handles incoming data strings simultaneously to improve efficiency. Just as two heads are better than one, so are two hands. Now when one is executing the other can be accessing the system bus or executing its own code. Adding to this favorable scenario, both AMD and Intel's dual-core flagships are 64-bit.
To utilize a dual core processor, the operating system must be able to recognize multi-threading and the software must have simultaneous multi-threadi0ng technology (SMT) written into its code. SMT enables parallel multi-threading wherein the cores are served multi-threaded instructions in parallel. Without SMT the software will only recognize one core. Adobe Photoshop is an example of SMT-aware software. SMT is also used with multi-processor systems common to servers.
An attractive value of dual core processors is that they do not require a new motherboard, but can be used in existing boards that feature the correct socket. For the average user the difference in performance will be most noticeable in multi-tasking until more software is SMT aware. Servers running multiple dual core processors will see an appreciable increase in performance.
Report to moderator 218.248.68.63 (?)
Knowledge is wealth...Try to Share it
Posts: 438
Threads: 322
Joined: Aug 2009
In a single-core r tradition nal processor the CPU is fed strings of instructions it must order, execute, and then selectively store in its cache for quick retrieval. When data outside the cache is required, it is retri eved through the system bus from random access memory (RAM) or from storage devices. Accessing th ese slows down performance to the maximum speed the bus, RAM or storage device will allow, which is far slower than the speed of the CPU. The situation is comp ounded when multi-tasking. In this case the processor must switch back and forth between two or more sets of data streams and programs. CPU resources are depleted and performance suffers.
In a dual core p rocessor each core handles incoming data strings simultaneously to improve efficiency. Just as two heads are better than one, so are two hands. Now when one is executing the other can be accessing the system bus or executing its own code. Adding to this favorable scenario, both AMD and Intel's dual-core flagships are 64-bit.
To utilize a dual core processor, the operating sy stem must be able to recognize multi-threading and the software must have simultaneous multi-threading technology (SMT) written into its code. SMT enables parallel multi-threading wherein the cores are served multi-threaded instructions in parallel. Without SMT the software will only recognize one core. Adobe Photoshop is an example of SMT-aware software. SMT is also used with multi-processor systems common to servers.
A dual core processor is different from a m ulti-processor system. In the latter there are two separate CPUs with their own resources. In the former, resources are shared and the cores re side on the same chip. A multi-processor system is faster than a system with a dual core processor, while a dual core system is faster than a single-core system, all else being equal.
An attractive va lue of dual core processors is that they do not require a new motherboard, but can be used in existing boards that feature the correct socket. For the average user the difference in performance will be most noticeable in multi-tasking until more software is SMT aware. Servers running multiple dual core processors will see an appreciable increase in performance.
check
http://en.wikipediawiki/Multi-core
Posts: 2,481
Threads: 1,434
Joined: Mar 2010
Posts: 5,362
Threads: 2,998
Joined: Feb 2011
[attachment=11699]
Abstract
Multi-core processors are growing as a new industry trend as single core processors rapidly reach the physical limits of possible complexity and speed. In the new Top500 supercomputer list, more than 20% processors belong to the multi-core processor family. However, without an in-depth study on application behaviors and trends on multi-core clusters, we might not be able to understand the characteristics of multi-core cluster in a comprehensive manner and hence not be able to get optimal performance. In this paper, we take on these challenges and design a set of experiments to study the impact of multi-core architecture on cluster computing. We choose to use one of the most advanced multi-core servers, Intel Bensley system with Woodcrest processors, as our evaluation platform, and use benchmarks including HPL, NAMD, and NAS as the applications to study. From our message distribution experiments, we find that on an average about 50% messages are transferred through intra-node communication, which is much higher than intuition. This trend indicates that optimizing intra- node communication is as important as optimizing inter- node communication in a multi-core cluster. We also observe that cache and memory contention may be a potential bottleneck in multi-core clusters, and communication middleware and applications should be multi-core aware to alleviate this problem. We demonstrate that multi-core aware algorithm, e.g. data tiling, improves benchmark execution time by up to 70%. We also compare the scalability of a multi-core cluster with that of a single-core cluster and find that the scalability of the multi-core cluster is promising.
INTRODUCTION
A processor is a unit that reads, decodes and executes the program instructions. The processors were originally developed with only one core. A core is a part of processor that actually performs
1. Fetching
2. Decoding
3. Executing an instruction as shown in Fig 1.
Single core processor is a processing system; is an Integrated Circuit (IC) which allows two or more individual and independent cores have been attached, on a single die. Placing two or more powerful computing cores on a single processor opens up a world of important new possibility. Each core has its own complete set of resources and may share on-die cache layers. As shown in fig 2 s in [1].
A single core processor can process only one instruction at a time. To improve the efficiency, processor commonly utilizes pipelines internally, which allow several instructions to be processed together. However they are still consumed into the pipeline at a time.
So it laid to evolution of Multi core processor; placing two or more powerful computing cores on a single processor opens up a world of important new possibility to increase the performance of the system as in
Need of Multi Core Processors
The difficulties in using a single core CPU gave birth to using the Multi core processors.
1. Difficult to make Single core clock frequency even higher in cost as shown in fig 3 as in [4].
The difficulty in raising clock frequency further results in improvement of performance but decreases reliability.
Doubling the frequency causes fourfold increase in power consumption. Calculated as Power = Capacitance * Voltage * Frequency.
2. Many New applications are Multi Threaded
3. General trend in Computer Architecture now-a-days shift towards Parallelism as in [8].
4. Deeply pipelined circuits which would lead to
a. Heat Problems
b. Speed of Light Problems
c. Large Design Teams necessary
d. Server Farm Need Expensive Air Conditioning
To overcome the above drawbacks of single core processor and to increase the performance of the system without increasing the power consumptions and with less complexity the need of Multi core processor raised.
