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Computer performance

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The performance of a personal computer is determined by a number of factors, all of which work together. Often a single item that is functioning poorly will cause a bottleneck resulting in poor performance.

CPU: The model of the CPU and its speed are the first factors that determine computer performance. Generally, the CPU so far outperforms the other components, that poor performance is usually due to other factors. One important factor in the performance of the CPU is the amount of on-board cache memory. If the CPU has sufficient cache memory it can queue future instructions and data in cache. Since access to cache memory is far faster than that to RAM, the overall processing performance is improved. On-board cache memory helps especially where the CPU is involved in processing of graphics.

RAM: If a computer does not have sufficient RAM, it has to make use of the hard disk to store intermediate data that it would normally store in RAM. This is referred to as virtual memory. Since hard disk access is much slower than access to RAM, this will slow down the computer. The more RAM a computer has, the less need there will be to make use of virtual memory.

Hard disk speed: In 2007, a typical PC hard disk might store between 160 GB and 750 GB of data, rotate at 7,200 to 10,000 revolutions per minute (RPM), and have a sequential media transfer rate of over 80 MB/s. The fastest hard disks spin at 15,000 RPM, and can achieve sequential media transfer speeds up to and beyond 110 MB/s. Mobile, i.e., Laptop hard disks, which are physically smaller than their desktop and enterprise counterparts, tend to be slower and have less capacity. In the 1990's, most spun at 4,200 RPM. In 2007 a typical mobile hard disk spins at 5,400 RPM and 7,200 RPM models are readily available for a slight price premium.

Number of applications: Modern computers are designed to run more than one application at a time and to allow applications to be working on multiple sets of data at the same time. For example, a user may be working on four documents at once. However, the more open applications and documents there are, the more this will place a burden on the processing power of the computer. For best performance, only open the applications and documents you need. Close others.

Graphics cards: The graphics card is the unit that converts the signals from the CPU into a form that can be displayed on the monitor. A good graphics card can take over many of the tasks of the CPU in generating the output. This leaves the CPU free to do other processing tasks. The quality of the graphics card is a key factor in the performance of a computer, yet is one which is often overlooked.

[edit] Benchmark

In computing, a benchmark is the result of running a computer program, a set of programs, or other operations, in order to assess the relative performance of an object, by running a number of standard tests and trials against it. The term, benchmark, is also commonly used for specially-designed benchmarking programs themselves. Benchmarking is usually associated with assessing performance characteristics of computer hardware, for example, the floating point operation performance of a CPU, but there are circumstances when the technique is also applicable to software. Software benchmarks are, for example, run against compilers or database management systems.

Benchmarks provide a method of comparing the performance of various subsystems across different chip/system architectures. Benchmarking is helpful in understanding how the database manager responds under varying conditions. You can create scenarios that test deadlock handling, utility performance, different methods of loading data, transaction rate characteristics as more users are added, and even the effect on the application of using a new release of the product.

[edit] Purpose

As computer architecture advanced, it became more and more difficult to compare the performance of various computer systems simply by looking at their specifications. Therefore, tests were developed that could be performed on different systems, allowing the results from these tests to be compared across different architectures. For example, while Intel Pentium 4 processors generally operate at a higher clock frequency than AMD Athlon XP processors, this does not necessarily translate to more computational power. In other words a 'slower' AMD processor, with regards to clock frequency, can perform as well on benchmark tests as an Intel processor operating at a higher frequency.

Benchmarks are designed to mimic a particular type of workload on a component or system. "Synthetic" benchmarks do this by specially-created programs that impose the workload on the component. "Application" benchmarks, instead, run actual real-world programs on the system. Whilst application benchmarks usually give a much better measure of real-world performance on a given system, synthetic benchmarks still have their use for testing out individual components, like a hard disk or networking device.

Benchmarks are particularly important in semiconductor microprocessor design, giving processor architects the ability to measure and make tradeoffs in microarchitectural decisions. For example, if a benchmark extracts the key algorithms of an application, it will contain the performance-sensitive aspects of that application. Running this much smaller "snippet" on a cycle-accurate simulator, can give clues on how to improve performance.

Computer manufacturers have a long history of trying to set up their systems to give unrealistically high performance on benchmark tests that is not replicated in real usage. For instance, during the 1980s some compilers could detect a specific mathematical operation used in a well-known floating-point benchmark and replace the operation with a mathematically-equivalent operation that was much faster. However, such a transformation was rarely useful outside the benchmark until the mid-1990s, when RISC and VLIW architectures emphasized the importance of compiler technology as it related to performance. Benchmarks are now regularly used by compiler companies to improve not only their own benchmark scores, but real application performance.

Manufacturers commonly report only those benchmarks (or aspects of benchmarks) that show their products in the best light. They also have been known to mis-represent the significance of benchmarks, again to show their products in the best possible light. Taken together, these practices are called bench-marketing. See this article for an excellent example of how application benchmarks can differ significantly from synthetic benchmarks.

[edit] Common benchmarks on the Windows platform

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