Computer Speed

1. Computer Speed

2. Determining the Speed of a Computer • Specifications • Examine the speed and size of the processor(s), memory, storage, and other components. • Benchmarks • See how fast the computer will perform certain tasks.

3. Specifications Processor Specifications Memory Specifications Bus Speed Storage Specifications Video Specifications

4. Processor Specifications • Processor specifications • Number of cores • More is better . With two cores the processor can handle two tasks simultaneously, with four cores it can handle four threads simultaneously. Typical programs are not divided into large amounts of separate threads so for example, a four core processor will probably only run slightly faster than a two core processor. • Writing software to take advantage of multiple cores is more difficult than writing software which does not. So IMHO, systems with more than four cores will probably not be worth the extra cost in the foreseeable future. I would not pay much extra for a system with more than two cores. • Speed (of core) • The speed of a processor is measured in (giga)hertz. For example a 2.5GH processor executes 2.5 billion cycles in one second. Typical computer instructions take several cycles to execute. For example if the average instruction took five cycles, then a 2.5GH processor could execute 500 million instructions per second. • The instruction set of a processor determines what instructions a computer can execute and the number of cycles that each takes. For this reason if processor A has a clock speed of 2.5GH and processor B has a clock speed of 2.0GH, it is not necessarily true that processor A is faster than processor B. • However, if processor A and processor B are of the same type then A is (probably) faster than B. Furthermore, most (personal) computers being sold today use processors from only two or three manufacturers. • Amount of cache • Processors contain cache (extra fast memory) which contain instructions and data to be processed. In general the more cache that a processor has the faster it will work.

5. Front Side Bus Speed The FSB transfers data between the CPU and the memory controller (Northbridge). The higher the FSB speed the faster that data can travel between memory and processor. What is desirable for a system is for the processor (and memory) to have no wait time. All other things being equal, the higher the FSB speed the faster data can be transferred and therefore the faster your computer will operate. The FSB speed must match the speed of the memory.

6. Memory Size • In general the more memory a computer has the faster it will operate – as long as the memory is being utilized. • For example, if you typically only run one or two programs at a time and they are i/o bound then adding extra memory will probably not increase the perceived speed of your system. • On most notebook computers and virtually all desktop computers, the memory is user-replaceable. On some computers such as the Macbook Air the memory is soldered to the logic board and cannot be replaced. • If the memory is user-replaceable, then the user can typically add more memory (with the possible cost of removing old memory).

7. Memory Speed Memory speed is measured in megahertz (mhz). The memory speed should match the speed of the FSB. If it is lower, then the computer will run at less than maximal speed. If it is higher it will probably run at maximal speed although for certain operations it may actually run at a lower speed.

8. Storage Implementation Storage is available in two implementations, disk drives and solid state (flash) drives. Flash drives are much faster than traditional disk drives. An article at http://www.tomshardware.com/reviews/ssd-notebook-portable,1913-5.htmlstates that boot time is cut in half by an SSD, program start time (Photoshop CS3 and Word 2008) is cut by a factor of three and loading a data file into Photoshop is cut by a factor of two. These tests were done on two macbook pros using a 5400rpm hard drive.

9. Storage Size In general the size of a hard drive does not affect the speed of a computer.

10. HP 8710p vs. macbook It’s on the Web site and looks at the typical specs given for two typical notebook computers from 2008. The principles are the same today.

11. Benchmarks Benchmarks measure the speed of a computer by counting the time it takes it to perform various tests. Benchmarks are numbers obtained by running a program or group of programs on a computer. Ideally benchmarks can be used to compare the performance of computers with different hardware and or software combinations. Benchmarks can be general in nature to assess overall performance or they can be designed to test one specific aspect of a computer's performance. In general, benchmarks only measure speed and give no importance to other aspects such as reliability, scability, and security. Benchmarks usually are obtained by running the program(s) multiple times and taking an average of their performance. Ordinarily, variability is not considered. Often "real world" benchmarks would consist of running a series of programs, often simultaneously, which simulate typical computer performance. For example, the computer might be set up to automatically load Word, Excel, and iTunes and start a particular song, while loading and spell checking a document and performing a series of calculations. The total time is then measured and compared to other computers. Benchmarks do not correct for actual use of computers in that they do not test with actual human interaction with the computer.

12. Effective Speed The speed of a computer is subjective and at times is irrelevant. For example, when using word processing software the speed of a computer is almost irrelevant since the biggest bottleneck is how fast the user types. The speed at which the user types depends on their typing ability and the speed at which they figure out what they want to type. Likewise the speed of browsing the Web will be primarily determined by the speed of the Internet connection and the amount of online traffic.

13. When you need fast computers • The speed of a computer largely comes into play under two circumstances: • How long does the system take to boot up? This is determined by what has to be done during the startup sequence. For most people, this speed slows down primarily because when you add new software to your computer, it typically adds to the boot up time by doing some stuff when the computer is starting. • Some software actually needs a high speed computer. • High end video games. • Video editing and rendering and 3D graphics. • Mathematical modeling including weather forcasting, engineering design and military simulations.

14. Speeding Up Your Computer (Hardware) • Component replacement • Processor’s can be replaced but usually this means buying an new computer. This also holds for the bus. • Memory – most computers can have their memory increased in size but not in speed. Usually this is a user upgrade and is very easy. You can look at the memory usage of your computer to see if it needs more memory. With today’s computers, I would opt for a minimum of 2GB of memory, with 4GB probably better. There are limits as to how much memory a computer can use. Currently prices for most systems are very cheap. • Storage – replacing a hard drive with an SSD will increase the speed substantially (see previous slides). Replacing the hard drive on a notebook may be somewhat difficult depending on the specific system. • Video can be upgraded on a desktop system but not a notebook system. Upgrading video will have little effect on the speed of your computer except for playing high-end games.

15. Speeding Up Your Computer (Hardware) Overclockingis the process of running the components (processor, memory) of the computer at a speed higher than they are rated for. This is not possible for most notebook systems. For desktop systems, particularly custom-built ones, this can be accomplished in the setup menu. Typically overclocking will cause the components to run hotter which will require better cooling and may result in erratic behavior of the system or component failure. I have never overclocked any of my computers.

16. Speeding Up Your Computer (Software) Many programs have components that will run when your computer is booted. This causes a computer which was ready to go 15 seconds after being turned on when it was new, to suddenly take a minute or more just to be ready to run. This problem can be alleviated by backing up your important data and possibly programs to an external source and then reinstalling your operating system from scratch. I used to do this once per year and still do it occasionally. This problem is worse on MS Windows than on OS X. If you do this be sure that you have copies of all the software that you want to keep along with the serial numbers that go with them. Disk defragmentation. When the disk is manipulated the files become fragmented. Fragmented files are slower to retrieve than contiguous files. Hard drives (but not SSDs!) should be defragmented on a regular basis. Typically this process may take an hour or more so this can be done when your computer is not in use such as when you are eating or sleeping. A disk with lots of free space (25% or more) is much easier and faster to defragment than a disk which is almost full. The disk on the computer in my office is 83% free and did not need any defragmentation when tested today by the standard windows defragmenter. It had been 6 months or more since it had been defragmented.