COSC 1401.004 TTH Mrs. Armstrong April 29, 1998 Buying a Computer Choosing the computer components What should I look for? First I will consider of the following components since the are the most important components to in order to help the computer work faster and better. – Processor (MHz)- Memory- CD-ROM Now, we have already established the necessity of a computer, and we have decided where one should go to purchase a computer. What else do we need to know? Well, a student buying a computer needs to know what to buy. What computer components should a student interested in a personal computer look for? What should I look for? In the initial stages of determining what sort of computer you need to get, at some point you need to ask yourself, what am I going to be using the computer for? Whether you intend to write papers for class, surf the World Wide idea of what the minimum requirements the computer needs to have. For this report, we are looking at the requirements of a typical student. That is, one who will be using a Windows version of some word processing program, as well as other programs found in the Microsoft Office97 package, anticipating internet use, animated presentations, high-level graphics and multitasking. What Type of Configuration Do You Need? Most computer systems, particularly the higher-end models, come in more than one configuration, desktop, mini tower, or tower. The configuration you chose depends mainly on the amount of expansion you plan to do in the future. Most tower configurations tend to have a greater amount of expandability than do desktop models as well as larger power supplies to handle additional internal components, such as multiple hard drives, CD-ROM drives, and tape drives. Also, the amount of space that you have in your office or home also needs to be taken into consideration. Tower configurations are made to be placed on the floor (except for the mini tower models), whereas desktop models are made to sit on the surface where the keyboard and monitor are located. Other than expandability and maybe a larger internal power supply, whether the computer is a desktop, mini tower, or tower configuration, it’s still the same computer. Here is a detailed look at some important components that one should consider: Processor (MHz) A processor is the “brain of your computer.” The megahertz (MHz) number means several things. First of all, the higher the number, the longer the computer will remain modern and the less likely it will be to become obsolete. The megahertz number represents the speed of your computer. Data flows through a computer under the control of a clock signal measured in Megahertz. The least expensive machines come with a 133 MHz Pentium. Over the last few years, Intel continued to reduce the price of CPU chips every three months, even when there was no competition. Eventually AMD and Cyrix reappeared with viable alternatives. An Intel Pentium with MMX is at least 10% faster than an Intel Pentium without it running at the same clock speed. The overall speed of a computer is affected by several things, but most notably the clock speed of the microprocessor and the speed and size of the instruction/data bus. The clock speed is the rate at which the microprocessor processes information and this is measure in millions of cycles per second (MHz). From slowest to the fastest there is the Pentium, Pentium with MMX technology, Pentium Pro, and the Pentium Pro II. If we compared the speed of these four Pentium class processors, assuming that they all had the same clock speed, it would go something like this. The 200 MHz Pentium processor with MMX is about 128% faster than the 200 MHz Pentium, the 200 MHz Pentium Pro is about 120% faster than the 200 MHz Pentium with MMX, and the 233 MHz Pentium Pro II is about 120% faster than the 200 MHz Pentium Pro (based on Intel’s data). What is MMX technology? MMX technology is based on a technique called Single-Instruction, Multiple-Data (SIMD). What this means is that microprocessors that use this technology receive 8 bytes of data as one package and this package of data is processed using a single instruction. Microprocessors that do not use the MMX technology would receive the 8 bytes of data, one at a time, and then would process each byte individually. Basically what this does is speeds up multimedia and communication software applications such as audio, graphics, video, and data communications. If one is only using the computer for word processing, creating simple spreadsheets, or just surfing the Web, much of a difference in the speed would not really be noticed. However, if one is using the computer to manipulate some graphic images, edit sound files, run a statistical analysis package, or compile some programming code written in Visual Basic or Visual C, then a big difference would be seen. So, if you only intend to use the computer for word processing, E-mail, and maybe an occasional spreadsheet or two, then the type of microprocessor that you get doesn’t really matter. Every machine has the power to handle ordinary applications. Most consumers will not notice the difference between a 200 MHz MMX machine and one with an older 133 MHz chip. What brand to get: What brand of microprocessor does the computer have, type and speed? Intel is the leading manufacturer of microprocessors, but microprocessors are also manufactured by other companies such as Cyrix and AMD. Although these other microprocessor chips are probably just as good as an Intel, there may be some subtle differences in them that might affect their performance working with other components and software. The type of microprocessor or the class of computer is important. Anything under a Pentium, such as a 386 or 486, is old technology. Since Pentium is a copyrighted name, other chip manufacturers have to call their microprocessor something else like 586. As far as the speed of the microprocessor goes, the current standard in computer systems being produced today is somewhere around a 166 to 200 MHz Pentium, although there are still a lot of the older ones being sold and several models faster than 200 MHz. Memory Also called main memory. The working space used by the computer to hold the program that is currently running, along with the data it needs, and to run programs and process data. The main memory is built from RAM chips. The amount of memory available determines the size of programs that can be run, and whether more than one program can be run at once. Main memory is temporary, and is lost when the computer is turned off. It is distinguished from more permanent internal memory (ROM) which contains the computer s essential programs, and storage (the disks and tapes which are used to store data). Random Access Memory The working memory of the computer. RAM is the memory used for storing data temporarily while working on it, running application programs, etc. “Random access” refers to the fact that any area of RAM can be accessed directly and immediately, in contrast to other media such as a magnetic tape where the tape must be wound to the point where the data is. RAM is called volatile memory; information in RAM will
disappear if the power is switched off before it is saved to disk. There is also a form of non-volatile RAM, which must be continually energized by a battery to maintain its content. The most common form of RAM is built from semiconductor integrated circuits. Random Access Memory cache Extremely fast memory chips that help the computer to operate faster by temporarily storing frequently-accessed or recently-accessed data. Internal cache (L1) is built into the CPU; external cache (L2) is on the motherboard. When the CPU needs data, it first checks the internal cache, which is the fastest source. If the data is not there, it checks the external cache. If the data still is not found, a search of the slower RAM must be made. Memory prices dropped spectacularly in 1996. Today machines come routinely with 16 megabytes of RAM, and high end machines have 32M. With memory selling for $5 per megabyte, it makes sense to upgrade even older machines. The disk is 100,000 times slower than memory. So if one has $300 to spend to make a system faster, one could buy a faster CPU, and get 1.5 times as much speed when the data is in memory. Or one could get more memory, and get 100,000 times as much speed when the data would previously pushed out to disk. It is quite easy to decide that extra memory is the safer choice. Ordinary PC memory uses Dynamic Random Access Memory or DRAM. Typically, such memory is rated to respond in 70 to 60 nanoseconds. A smaller amount of memory may be added to the system as an “external” or “second level” cache. This is made of faster Static RAM or SRAM. The later 486 models used “Fast Paged” memory. Most Pentium computers support both Fast Paged and a slightly better technology called EDO. The latest technology, supported by MMX systems, is called SDRAM. SIMM and DIMM Memory There are currently two different types of slots on Pentium class motherboards where you can install additional memory, the 72-pin SIMM (Single In-line Memory Module) and the 168-pin DIMM (Dual In-line Memory Module) slots. Memory modules are available in the following three basic classifications: + DRAM (Dynamic Random Access Memory) which is the slowest.+ EDO (Extended Data Out) which was the dominant type of memory used between 1995 through late 1996.+ SDRAM (Synchronous DRAM) which is the current standard and the fasted of the three type of DRAM memory. Cache Memory The cache is a high speed memory area that keeps a copy of the most recently used data in main memory. Most programs go back and re-execute the same instructions, or update the same numbers, and the cache provides better performance. A modern PC has two levels of cache. A First Level (L1) Cache is contained within the CPU chip itself. The Intel 486 family was designed with 8K of first level cache memory. Subsequent Intel and non-Intel computer designs have 16K or even 32K internal cache. The first level cache is best, because it can be used by the internal pipeline instruction processing components of the CPU. A 486 can add two numbers in two clock ticks, provided that both numbers are held inside the CPU. When one of the numbers is outside the CPU chip, the instruction takes a minimum of 4 clock ticks no matter how fast the external memory might be. An external or Second Level (L2) Cache can be installed with SRAM chips on the mainboard. SRAM responds faster than DRAM. Usually SRAM can deliver data in one or two external clock ticks. However, the 486 or Pentium have still been substantially delayed just to set up any type of external memory reference. CD-ROM Compact Disc Read-Only Memory. An optical disk that is physically the same as an audio CD, but contains computer data. Storage capacity is about 680 megabytes. CD- ROMs are interchangeable between different types of computers. Digital Versatile Disc A Digital Versatile Disc (DVD) is an optical, high capacity version of the CD-ROM. Up to now the CD-ROM has been limited to a maximum storage capacity of 650 MB of data, the new DVD discs will be able to store all of the information on 25 CD-ROMs and then some. There are currently three versions of the DVD, a standard single-layer, single-sided disc that can store 4.7 GB of data, a two-layer, single-sided disc that can store 8.5 GB, and a two-layer, double-sided disc that can store 17 GB. SCSI/ATAPI/Proprietry SCSI CD-ROM drives plug into a SCSI card. ATAPI CD-ROM drives plug into an IDE card. They need their own cards, but they’re pretty rare now. Speed CD-ROM drives are referred to 6, 8, 12, 24, etc. speed. That refers to the number of 150 kilobytes the drive can transfer each second (so a double-speed transfers 300kb/sec). Based on the type of things you plan to do with your computer, you will have a set of minimum requirements that the software must have in order to do the tasks that you plan to perform at a reasonable or acceptable speed (I define an acceptable speed as being able to do a spell check in a word processing application faster than I can thumb through Webster’s Dictionary myself). To find out what types of systems are available, the first place to start is by picking up a copy of one of the many computer magazines on the market or visiting their Web site, such as PC World, PC Magazine, or Byte, or one of the trade newspapers, such as InfoWorld or PC Week. These magazines and newspapers usually have articles comparing the various types and brands of computers as well as other components, such as monitors, modems, printers, and software. But beware, don’t put too much into the rating systems that these magazines and newspapers use, since many of the computer manufacturers pay these companies for advertising. Use these ratings as a way to narrow down your list of options. One of the best sources for information is your friends and family members. See if any of them have a system similar to what you want to buy. Check to see if they have had any trouble with their system or have ever tried to get technical support from the system’s manufacturer. Also see if they have ever had any compatibility problems with any software applications or hardware. The main things to look for are compatibility problems with the operating system, printers, and CD-ROM drives. If they have had compatibility problems, see what steps they took to get the problems resolved and how long it took to get the system working again. And finally, see if they would buy another computer system from this company. Another good place to check for information is the World Wide Web. Start your favorite Web browser, then in the locator, enter a URL in the format www.Company.com, replacing the word “Company” with the name of the company, such as www.compaq.com (Compaq), www.ibm.com (IBM), www.gw2k.com (Gateway 2000), or www.dell.com (Dell). Usually these hardware manufacturers, as well as most of the software and components companies, will have a complete listing of their line of products as well as the specifications. In addition to the World Wide Web, information on the various types of computer systems and software can also be found in the USENET newsgroups. I recommend the following components for a new personal computer used by a typical college student for school and everyday life:+ 200 MHz Pentium MMX processor, preferably a 233 MHz Pentium II+ at least 32 MB (as much as possible) of RAM and 512K of external cache memory+ a fast hard drive of at least 3.2 GB, preferably 4 GB+ at least a 24X CD ROM+ 33.6-kbps modem with voice and fax capability, 56-kbps if your provider supports x2+ 100 MB removable storage disk+ Monitor, Keyboard and Mouse is really subject to personal preference decide what you want and need based on all the information Summary Once one determines what one needs the computer for, the next question that one needs to ask is how much money they can afford to spend. One should buy as much PC as one can afford. Don’t cut corners on the main system unit (monitor, microprocessor, memory, disk space, etc.). Remember, this system is going to last at least 2 or 3 years or maybe more and you don’t want to start running out of disk space or memory in the first week that you have it because you trimmed down the amount of memory or got a smaller hard drive. Remember, you get what you pay for. Be realistic, smart and cautious. Make sure you know exactly what you want and how to get it. Most importantly: Have fun !!!