1.4: Processor and System Performance

Introduction

This section introduces the learners to the processor and system performance. Material on the characteristics of the processor and system performance as well as the components that determine the system performance is provided .

Activity Details

The performance of a computer is dependent on how well it works together as a whole. Continually upgrading one part of the computer while leaving outdated parts installed will not improve performance much, if at all. The processor, memory and video card are the most important components when determining performance inside a computer.

The following are some of the most important parts of the computer regarding its speed and computing power;

1. Clock speed (Processor speed);

is often played up to be the major factor in a computer’s overall performance. In rare cases this is true, but an average user rarely uses 100 percent of his Central Processing Unit’s power (CPU). Things like encoding video or encrypting files, or anything that computes large, complex, numbers requires a lot of processor power. Most users spend most of their time typing, reading email or viewing web pages. During this time, the computer’s CPU is probably hovering around 1 or 2 percent of it’s total speed. Startup time is probably the only time the CPU is under stress, and even then it’s often limited due to the hard drive speed.

2. System RAM speed and size;

The amount and speed of the RAM in your computer makes a huge difference in how your computer performs. If you are trying to run Windows XP with 64 MB of RAM it probably won’t even work. When the computer uses up all available RAM it has to start using the hard drive to cache data, which is much slower. The constant transfer of data between RAM and virtual memory (hard drive memory) slows a computer down considerably. Especially when trying to load applications or files. The two types differ in the technology they use to hold data, dynamic RAM being the more common type. Dynamic RAM needs to be refreshed thousands of times per second.

Static RAM does not need to be refreshed, which makes it faster; but it is also more expensive than dynamic RAM. Both types of RAM are volatile, meaning that they lose their contents when the power is turned off.

3. Disk speed and size;

Is the biggest factor in your computer’s performance is the hard disk speed. How fast the hard drive can find (average seek time), read, write, and transfer data will make a big difference in the way your computer performs. Most hard drives today spin at 7,200 RPMS, older models and laptops still spin at 5,200 RPMS, which is one reason laptops often appear sluggish to a desktop equivalent. The size of your hard drive plays a very little role in the performance of a computer. As long as you have enough free space for virtual memory and keep the disk defragmented it will perform well no matter what the size.

4. Video card - (onboard video RAM, chip type and speed);

Whenever your computer puts an image on the screen something has to render it. If a computer is doing this with software it is often slow and will affect the performance of the rest of the computer. Also, the image will not be rendered as crisp or as smoothly in the case of video. Even a low-end video card will significantly improve the performance of the computer by taking the large task of rendering the images on the screen from the CPU to the graphics card. If you work with large image files, video or play games you will want a higher end video card. Video cards use their own RAM called Video RAM. The more Video RAM a computer has the more textures and images the card can remember at a time. High end graphics cards for desktops now come with up to 64 megabytes of Video RAM, Laptops often only have 8 or 16 megabytes of Video RAM.

5. Others include memory and system buses

Latency memory, performance and efficiency

Is a time delay between the cause and the effect of some physical change in the system being observed. Latency is a result of the limited velocity with which any physical interaction can take place.

This velocity is always lower or equal to speed of light. Therefore, every physical system that has spatial dimensions different from zero will experience some sort of latency. The precise definition of latency depends on the system being observed and the nature of stimulation. In communications, the lower limit of latency is determined by the medium being used for communications. In reliable two- way communication systems, latency limits the maximum rate that information can be transmitted, as there is often a limit on the amount of information that is “in-flight” at any one moment. In the field of human-machine interaction, perceptible latency (delay between what the user commands and when the computer provides the results) has a strong effect on user satisfaction and usability.

Computers run sets of instructions called a process. In operating systems, the execution of the process can be postponed if other processes are also executing. In addition, the operating system can schedule when to perform the action that the process is commanding.

For example, suppose a process commands that a computer card’s voltage output be set high- low-high-low and so on at a rate of 1000 Hz.. The operating system may choose to adjust the scheduling of each transition (high-low or low-high) based on an internal clock.

The latency is the delay between the process instruction commanding the transition and the hardware actually transitioning the voltage from high to low or low to high. System designers building real-time computing systems want to guarantee worst-case response. That is easier to do when the CPU has low interrupt latency and when it has deterministic response.

Caches

Cache memory, also called CPU memory, is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. This memory is typically integrated directly with the CPU chip or placed on a separate chip that has a separate bus interconnect with the CPU. The basic purpose of cache memory is to store program instructions that are frequently re-referenced by software during operation. Fast access to these instructions increases the overall speed of the software program. Most programs use very few resources once they have been opened and operated for a time, mainly because frequently re-referenced instructions tend to be cached. This explains why measurements of system performance in computers with slower processors but larger caches tend to be faster than measurements of system performance in computers with faster processors but more limited cache space.

Conclusion

This section covered the processor and system, the characteristics of the components that determine system performance.

Assessment

1. Discuss system performance

Computer performance is characterized by the amount of useful work accomplished by a computer system or computer network compared to the time and resources used. Depending on the context, high computer performance may involve one or more of the following: Short response time for a given piece of work.

• Short response time for a given piece of work

• High throughput (rate of processing work)

• Low utilization of computing resource(s)

• High availability of the computing system or application

• Fast (or highly compact) data compression and decompression

• High bandwidth

• Short data transmission time