Chapter 5 Considerations in Buying a Computer Questions to decide Microprocessor or CPU Two families: Intel x86 processors (PCs and compatibles) and Motorola 68000 (Apple Macintosh). Older x86 computers were 8086 and 8088 (original PC), 80286, 80386, 80486. Newer Intel computers use the Pentium processor. All software that runs on the older IBMs will run on the Pentium - however, the converse is not true - i.e. software designed for Pentium will not run on the older IBMs. Part is due to the fact that the machine code uses instructions not available on older processors - other reason is that the software uses more resources - memory - than was available on older machines. Software written for the Motorola 68000 will definitely not run on the x86 machines and vice- versa. The PowerPC microprocessor is an attempt to provide both computing platforms in one chip. It is used by IBM and Macintosh in their power computers. It cannot directly execute x86 or 68000 instructions, but you can use it with an emulator to run programs in either instruction set. An emulator is software or hardware that enables one mircroporcessor to behave as if it were another. If you buy a Mac PowerPC, it comes with the 68000 emulator and you can purchase the IBM emulator as an add-on. Today, if you buy an IBM compatible, you should buy a Pentium processor with a clock speed of 100 MHz or better. Some rivals to Intel market chips that work the same as Pentiums and are called 586 or 686 processors - generally less expensive. A good rule of thumb is not to buy the most expensive, latest computer because you are paying a premium price for it. If current processor speeds are 100 MHZ, 133 MHz and 166 MHz, buy the 100 MHz processor (2 grades down from the best). Also, if you are buying for a company, keep in mind that the computer will be effectively obsolete and need to be replaced in 2-3 years - even if you bought the best. For these reasons, buy a computer that is a couple of grades down from the best available and don't pay much attention to future expansion and upgrade capability - chances are it will be more cost- effective to replace it than to upgrade it. RAM cache - with today's faster processors it makes no sense to have the computer waiting to retrieve one value at a time from RAM memory. They can process data faster than it can be retreived from memory. For this reason, you need a RAM cache of at least 256 K bytes. This adds about $100 to the cost of a computer. Memory To run Windows '95, you should have at least 8 to 16 Megabytes of memory. Today's memory prices are the lowest they have ever been - about $50 for 4 Megabytes of memory. This used to be the price for one Megabyte. It is relatively easy to add memory to a computer. However, you must be careful about static electricity if you attempt to do this. It is very easy to blow out your motherboard by touching it. Floppy disk drive One 3.5 inch floppy disk drive is enough. With today's increased memory sizes, you can copy a disk with just one floppy. The diskcopy utility reads the old disk contents into memory - you insert the new disk and it writes the old disk contents on the new disk. CD-ROM drive New software is increasingly available on CDs. CD drives come in quad-speed (4x), six-speed (6x) and eight-speed (8x) versions. If you are using multimedia applications, you need the fastest drive available (8x). Hard Drives Factors to consider are storage capacity, speed to access and transfer data, controller type, size of disk cache, and bus speed. The capacity should be at least 1 Gigabyte (1000 Megabytes). Access times should be 10-12 milliseconds or better. The controller is used to position the read/write heads and is often inside the disk. Older computers used IDE controllers (integrated device electronics). Today's computers use EIDE (Enhanced Integrated Device Electronics) or SCSI (pronounced "scuzzy") drives. The SCSI controller is not part of the disk. SCSI controllers are a little better and are more expensive. They have an extra advantage in that you can usually connect multiple scuzzy devices (for example, an external backup removable disk drive and an internal hard drive) to the same controller since it is not part of the device. A disk cache improves performance - fewer disk accesses required to retrieve data. Also, a local bus for transferring data between disk and memory improves performance. Buses - used for transporting data between the CPU, memory, and devices in the expansion slots. Local buses provide high-speed data transfer to display and storage devices. Some expansion slots are connected to slower buses (16 bits at a time at 8MHz) and others are connected to faster local buses (32 bits at a time at 33-66 MHz). Several slots will be filled with devices currently connected to your computer. Make sure you have a couple of expansion slots free for extra devices you might add later. Monitors screen size should probably be 15 inches or larger (measured diagonally). 17 inch monitors are popular for those who tend to have several windows open simultaneously. Dot pitch is a measure of image clarity - distance between dots on the screen - smaller numbers are better - 0.28 inches is typical. Maximum resolution is the number of dots on the screen. Typically 1024 x 768 (1024 across, 768 down). A non-interlaced monitor has less flicker than an interlaced monitor. Non-interlaced means that all the dots on the screen are refreshed during each pass. Interlaced monitors refresh only 1/2 the dots on a screen during each pass, so it requires 2 passes to refresh all the dots, causing flicker for higher resolution screens. Energy compliant monitors and computers use less energy by switching to lower power standby mode after a period of inactivity. Low-radiation monitors emit less radiation and may be safer. Video adapters or cards (or graphics cards) drive the monitor. They provide a data path between the micorprocessor and monitor. Accelerated video adapters connected to a local high-speed bus provide best graphics. There are also VGA adapters and Super VGA adapters. Super VGA adapters support higher resolution screens. The amount of memory on a video card can vary. You should have at least 1 Megabyte of memory and 4 Megabytes for higher resolution displays. Sound Card Used for games or multimedia applications. Provides better sound quality, 8-bit or 16-bit sound cards are available. Look for sound- blasted compatible cards. Modem The important criterion is baud rate in bits per second. Latest modems run 33,600 bps. Temple's network now accepts 28,000 bps. You can use a faster modem and set it tot transmit at a slower speed. FAX/Modem is a modem that can send a document in your computer as a fax transmission to a fax machine. Similarly, it can receive a fax tranmission and display it. You can also print it. Bundled software An important consideration in buying a computer. The more the better. Printers 3 kinds - dot matrix - older, noisy, less resolution - print multiple part forms. They print by pressing a column of metal pins against a ribbon, thereby placing an ink dot on the paper. The print head moves across the page, forming letters as it goes. They more pins, the better the resolution. 24-pins give acceptable letter images. ink-jet - print by spraking ink onto a paper. The print head is a matrix of nozzles used to form a single letter (20 x 20 matrix is common). Color-ink jet printers are economical and a good value. Ink-jet printers provide "near laser" quality at a more affordable price. Laser printers - best quality. A laser charges magnetizable particles on a drum. The charged particles pick up a powdery black substance called toner which is deposited on the paper as it rolls through the drum. Most expensive to buy and operate - Need to replace toner cartridges periodically. They are expensive. Notebook computers - Have the advantage of portability. Disadvantage is that they are expensive compared to desktop computers, keyboards are not as comfortable to use, displays are smaller and hard to view especially in sunlight, moving the cursor is usually a little more difficult using the built-in mouse or mouse-substitute. Also, batteries don't last more than a few hours and computers are relatively heavy (7 pounds or so) if they have floppy disks and CD ROM drives built-in. Instead of expansion slots inside the computer, notebook computers use a PCMCIA slot (personal computer memory card international association) into which you can slide a PCMCIA card to add a device built-into the card. For example, you can have a card that adds memory, or a card that is a modem or a disk drive. Notebooks use liquid crystal display (LCD) screens instead of monitors. It is a flat panel built into the top of the computer. Passive matrix screens are cheaper but not as good as active matrix screens for graphics. Screens are in color or black and white (monochrome). Most notebooks have a VGA or SVGA port so you can connect to a monitor on your desk. Some computers come with docking stations which contain CD-ROM drives, speakers, for multimedia use. You insert your notebook in the docking station when you want to use these devices. Instead of a mouse, a notebook uses a built-in trackball which you turn to move the cursor. Others have a track point or a small touch pad. Software Products Software is produced by software publishers. Before being released, the software is tested in-house by testing experts (called alpha testing). Next, it is sent out to many potential users for further use and testing (beta testing). When all the bugs discovered at this point are corrected, it is released to the general public as Version 1.0. As users report problems, they are fixed and a new revision of the software product is released (Version 1.1). Usually they are given at no cost to users of the software. If new bugs occur or minor changes are made additional revisions will be created (Versions 1.2, 1.3, etc.) When it is time for a significant upgrade, a new version (or release) will be offered (Version 2.0). Users of the original version are usually offered the privilege of upgrading for a small price compared to buying the new release as a new user. It is best to wait a few months until the bugs have been found and corrected before updating. Where to buy Hardware and Software Retail stores Offer a wide variety of different kinds of computers and software. Generally available for support if you have problems. Mail-order suppliers If you have some experience with computers you can buy a computer through the mail and save a substantial amount. Often large mail-order suppliers have their own house-brand of computers which perform as well as the major computer manufacturers for less money. Be wary though because sometimes the components in lower-priced computers are not as good quality. Direct from Manufacturer Both Gateway and Dell computers sell their computers directly. You can save money by buying direct. Temple University offers Gateway computers and others at a discount. See Computer Services for more info. For product reviews and comparisons of different brands - see PC Magazine or Byte Magazine before buying.