Buying a Computer?

A few things you should know
and terms you should understand

Advertisements for computers usually contain terms the computer novice does not understand. The following is intended as a brief explanation of those terms, and what you should be on the look-out for.

Text on a grey background is nerdy details you probably don't want to know, but probably should, if you really want to understand what you are dealing with.

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Contents

Click to jump to a topic. You should be aware of the following terms and what they mean; explanations and definitions follow:

• QUICK TIPS - things you need to know
• Bits, Bytes, Kilobytes, Megabytes, Gigabytes, Terabytes...
• Motherboard, or mbd, and the FSB (Front Side Bus)
• CPU and Mhz (megaherz)
• RAM, or memory
• Cache, or Cache RAM
• Hard drive or Hard Disk (HDD, or HD)
• CD-ROM, or CD and DVD
• Video card, or display
• Sound card
• Modem
• Network card
• Hardware and Software
• Operating System, or OS

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Quick Tips - Things You Really Need To Know

If you are buying a new computer, here is my advice:

1. Buy a cheap one

2. Think about what you want to use it for

3. Useless extras and upgrades

4. Warranties

5. Warranty Replacement

6. How upgradable is it?

7. Be sure you get copies of the drivers and the Operating System

8. Avoid name-brand systems

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Bits, Bytes, Kilobytes, Megabytes, Gigabytes, Terabytes...

Kilobytes, Megabytes, Gigabytes, etc., are measurements of data quantity. The terms are used to indicate the storage capacity of several types of hardware, including all kinds of RAM (system RAM, cache RAM, flash cards, memory sticks) and disk size (floppy, hard, CD, DVD, Zip).

Computers run on electricity, which has basically two states, on or off; a bit is the smallest unit a computer can deal with, it's either a one or a zero (on or off). Computers therefore count in binary, as opposed to base 10, like most people do. For reasons that don't concern us here, bits are generally referred to in groups of eight (8). Eight bits make one byte. A thousand bytes is one kilobyte, a million bytes is one megabyte, a billion bytes is one gigabyte. In tabular form:

So many of these...	...Make this many of these
a one or a zero...	...is one bit
8 bits	one byte
1,000 bytes*	1 kilobyte
1,000,000 bytes*	1 megabyte
1,000,000,000 bytes*	1 gigabyte

*This is not quite accurate, but good enough for our purposes. A kilobyte is in fact 1,024 bytes, because it is two to the tenth, or 2^10, or 2¹⁰. Likewise, a megabyte is 1,048,576 bytes (1024²), and a gigabyte is 1,073,741,824 bytes (1024³).

These numbers by themselves probably aren't very enlightening, but consider:

• this document (web page) you are looking at would be about 7 pages printed, and it is 27Kb (27,000 bytes)
• you could fit 50 copies of it on a floppy disk, or 2 million copies on a 60Gb hard drive
• the same information as a word processor document would be rather longer, probably 50Kb (50,000 bytes)
• you could fit 30 copies of it on a floppy disk, or 1.4 million copies on a 60Gb hard drive
• with data compression, the entire Bible (Old and New Testaments) will fit on a floppy disk as plain text (no fancy formatting, no bold, no italics, etc.)
• MP3 sound files vary somewhat, but they are typically between 1 and 2Mb per minute of music, so a 60Gb hard drive could hold about 10,000 3-minute songs

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Motherboard, or mbd, and the FSB (Front Side Bus)

The motherboard provides the physical connection between all the various bits of hardware (see Hardware, below). It has a socket for the CPU(s), connectors for the mouse, keyboard, and printer, as well as slots for RAM and peripheral cards (video, sound, modem, etc.).

Like CPUs, mbds have a Mhz rating (see CPU and Mhz, below), but with a difference: the Mhz rating of a mbd can be changed by means of switches called jumpers, or by other methods. Most new mbds automatically detect what setting they should use, so you don't need to set jumpers. The faster a mbd is capable of running, the better. The mbd speed is usually expressed as the speed of the Front Side Bus (FSB), which is actually the physical connection (called a bus) between the CPU and the main system RAM. There are other buses, but this is considered the most important one for overall performance.

Commonly available motherboards can run at 133, 266, 400, 533, and up to 800Mhz (apparently this may involve fudging some numbers, but I need to do more research on it); anything at the low end of that range is rather old product. Stay away. The speed at which the mbd should be set depends on what CPU is on it, and what type of RAM. For example a typical mbd can be set to 66, 100, 133, or 266Mhz etc., and then "clocked" to run at a multiple of that speed. An old 75Mhz CPU required a mbd set at 50Mhz x 1.5; a 100Mhz CPU required 66Mhz x 1.5, etc. The vast majority of new mbds will detect the CPU and the RAM, so you will not have to set anything. Here are some examples of mbd and CPU combinations:

CPU speed	Mbd speed	Clock ratio
75Mhz	50Mhz	1.5
150Mhz	60Mhz	2.5
133Mhz	66Mhz	2.0
600Mhz	66Mhz	9.0
600Mhz	133Mhz	4.5
733Mhz	133Mhz	5.5
2000Mhz	266Mhz	7.5

There are several points to ponder in this table:

• A tolerance of plus or minus 10% is acceptable: 266Mhz x 7.5 = 1995, which is close enough to 2000 that neither the CPU nor mbd will care.
• Certain CPUs come in several models; for example, a 600Mhz chip may have three variants, designed to run at multiples of 66, or 100, or 133Mhz.
• A system with a 133Mhz CPU is actually faster than one with a 150Mhz CPU, because the 133 runs at 66 x 2, as opposed to 60 x 2.5.
• Keeping in mind the above statement: all Celeron CPUs below 1Ghz have to run at a multiple of 66Mhz, so don't be fooled: a system with a Celeron 733 (66Mhz x 11) is not going to be faster than a system with a Pentium III 600 (100Mhz x 6, or 133Mhz x 4.5).

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CPU and Mhz

CPU stands for Central Processing Unit. This is the "brain" of any computer, where the work is done. Mhz stands for Megahertz. In relation to CPUs, Mhz means "X million clock cycles per second". That is, a 300Mhz CPU goes through three hundred million clock cycles per second. The CPU fits into a socket on the motherboard. There are many types of sockets and CPUs.

Note: Many people mistakenly think that this means the CPU performs X million calculations per second, which is not the case. Most instructions and calculations require more than a single clock cycle to execute, so no CPU is ever actually performing X million (=its Mhz rating) calculations per second.

For the most part, the higher the Mhz rating, the faster the CPU (but see the table and comments above, under Motherboard). These days, do not even consider buying a new computer with a CPU slower than about 1500Mhz (=1.5Ghz). Anything slower is a product that has been sitting on the shelf collecting dust for some time, and may have a very limited warranty, or none.

Celeron vs Pentium II/III/IV: They are pretty much exactly the same CPU; the main differences concern their cache RAM (see Cache, below), and how fast the mbd can be set.

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RAM, or Memory

RAM stands for Random Access Memory, and the more you have, the better. RAM is measured in megabytes, or millions of bytes (a byte is an eight-digit binary number). It is abbreviated as MB or Mb or M. You do not want a (new) computer with less than 256Mb of RAM.

RAM is where programs are when they are running. When you start a program, it is loaded into RAM, where it sits until you close that program or turn off the machine (anything in RAM is lost when the power is turned off). Games and anything involving graphics or sounds require lots of RAM to run properly. Without enough RAM, moving images will be jerky, and sounds will be choppy, or the machine may just freeze. The more RAM you have, the faster everything will run. There is no such thing as too much RAM.

There are several types of RAM. The problem with RAM (as with computers in general) is that the standards change rapidly, and the price constantly fluctuates. RAM is bought and sold like stocks I've heard. To be honest, I don't know what the best type of RAM is anymore. All new RAM is extremely fast. I suspect only benchmarking software would be able to tell the difference. Perhaps you know some guru who can tell you what the best RAM to buy is this week. Then you can tell me.

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Cache, or Cache RAM

Cache is high-speed RAM that works in conjunction with the other RAM. There are two types: L1 and L2. L1 means level 1, and is built into the CPU. Pentium II/III/IV CPUs may have 256 kilobytes (Kb), or as much as 1Mb; Celeron CPUs have 128Kb, or none. Any Celeron from the 300A up has 128Kb. Older CPUs have varying amounts. L2 means (guess what) level 2, and is on the motherboard. Most mbds sold today have 1Mb or 512Kb cache, but some may only have 256Kb (WARNING: old product).

When any computer is running, data is constantly being shuffled back and forth. Cache can be thought of as temporary holding areas for data waiting to be used or waiting until it is needed. Since accessing data from RAM is much faster than reading it off the hard drive, cache significantly improves system performance. As with RAM (above), the more cache of both types, the better.

Celeron cache vs Pentium II/III/IV cache: Celeron CPUs have less cache RAM, but the cache RAM runs at the same speed as the CPU in some, at least; i.e., data in the cache is processed/accessed at 700Mhz, whatever the speed of the CPU is. Pentium II and up CPUs have much more cache RAM, but the cache RAM runs at the same speed as the motherboard, that is, 100Mhz, or 133Mhz etc.

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Hard drive, or hdd, or hd

The hard drive of a computer is basically storage space, like a book shelf or filing cabinet. It is inside the computer, hidden from view. Hard drive capacity used to be measured in megabytes, like RAM. Drives today have gotten so big they are measured in gigabytes (GB, or Gb, or G), or billions of bytes, and terabytes (TB, Tb, T), trillions of bytes.

How much storage space do you need? That depends on what you want to do, but I wouldn't be concerned about the size of the drive a computer comes with. External USB drives are cheap (50 cents per gigabyte or less is not unusual). You can always buy a bigger hard drive in the future, or simply add another one when you need it.

Any mbd sold today should be able to support up to four internal hard drives or more. Be aware that DVDs, CD-ROMs and burners count as hard drives, in most systems. You can also purchase add-in controller cards that will allow you to connect several more hard drives (how many depends on the particular card and your motherboard).

Note: Your hard drive is not normally considered to be "memory" (although technically "memory" is any kind of electronic data storage). They are two quite different things (see RAM, above). I, and several other techs I know, have more than once been thoroughly baffled by end users' problems with "memory", which turn out to be problems with the hard drive.

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CD-ROM, or CD, DVD

This is much the same as a CD player. A computer CD-ROM can play any music disk, but it can also read data disks, which your music CD player cannot. Computer CD-ROMs are rated with a number followed by an "x", like 20x, 40x, 50x, and are referred to as "twenty speed", "forty speed", etc. Avoid anything slower than 50x; like slower CPUs, it will be old product, perhaps already out of warranty.

The first CD-ROMs had a maximum data transfer rate of 150 kilobytes per second under ideal conditions (that is a "1x" CD-ROM, or "one speed"). Theoretically, then, a 50x can handle data transfer rates of 50 x 150Kb/sec = 7.5 Megabytes per second, although the reality is a little more complicated, and depends on the other hardware in the system.

DVD players: A DVD player is a CD-ROM on steroids. A standard CD holds 700Mb of data, but DVD disks can hold several times that much (4Gb+, 8Gb+), and the data transfer rate is faster than the fastest CD-ROM.

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Video card, Graphics card, or display

The video card is what translates the signal from the computer into something you can see on the monitor screen. There are three types, which fit into three different types of slots on the mbd: ISA, PCI, and AGP. If you see a (supposedly) new machine advertised with an ISA video card, run away: ISA video cards are out-dated technology. I would also be just a little suspicious (but see below) of a "new" computer with a PCI video card. AGP was the best (fastest) for a time, but now there is PCIe.

Video cards have their own RAM, anywhere from 1Mb to 256Mb or more. Generally, the more the better, but it depends on what you want to do. If you want to play high-end games or anything else graphics-intensive, get the best you can. However, if you are doing mostly business-type things (word processing, spreadsheets, databases), there is no point in getting a 512Mb card - you will never use more than a fraction of that 512Mb. A cheaper card would be fine.

Note: Beware of motherboards with built-in video. If there is no way to disable the on-board video, you will never be able to upgrade. Also, on-board video will more than likely use regular RAM, thus taking resources away from the rest of the system.

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Sound card

The sound card translates data of various types into a signal which can be fed into speakers. There are two types, ISA and PCI, but you're not likely to see an ISA sound card now. There is nothing necessarily shameful about ISA sound cards. I am still using an ancient Sound Blaster 16 ISA card in one equally ancient machine, and it sounds fine to me, but:

Sound is very much a matter of personal taste. What sounds fine to one person may sound awful to someone else. Sound cards cost anywhere from about $20 up into the hundreds. Your best bet is to go to a few computer stores and listen to several different cards with several different types of speakers. If you do not plan on using your computer as a stereo system or movie theatre, there is no point in buying expensive speakers and a high-end sound card. If all you want is to be able to hear the noises the machine makes, and basic audio from movie or music clips, get the cheapest sound card and speakers possible. You can always upgrade later.

Note: Beware of motherboards with built-in sound. On-board sound does not use system RAM like on-board video, but if there is no way to disable the on-board sound, you can never upgrade.

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Modem

A modem can be used for three things:

• connecting to the internet and email etc (becoming rare)
• sending and receiving faxes (the paperless fax - unless you decide to print them)
• acting as an answering machine

A modem (short for modulator-demodulator) converts (digital) computer data into a format (analog) which can be transmitted over an ordinary telephone line. There has to be another modem at the other end of the line (in another computer) to convert the data back into (digital) computer format. It's not the most efficient way to carry data, but remember, telephone lines were never intended for any such thing.

Like sound cards, there are two types, ISA and PCI, although you're unlikely to see ISA models for sale. PCI modems are faster (at least in theory, because PCI slots are faster), but there are other factors involved, like how much RAM you have, who your ISP is and what their hardware is, etc.

Modems are rated according to how fast they can transmit data under ideal conditions, measured in kilobits per second (yes, kilobits, not kilobytes), or kbps, or simply k. The fastest modems today are 56k (currently the industry standard), which translates to about 7 kilobytes per second. Your actual rate of data transfer while connected may be considerably more or considerably less than 56k, depending on how good your connection is, and how busy the network is, and other factors, mostly beyond your control.

Any modem slower than 56k is old and out-of-date; avoid them. There are several types of 56k modem which reflect several ways of handling data. You may encounter terms like the "X2", "flex", or "v90" standards. Most modems these days support more than one standard (or all of them). If you are going to use a modem for an internet connection (not likely these days), decide which Internet Service Provider (ISP) you are going to sign on with, and find out what types and speeds of modem they support.

What about cable modems? A different animal altogether. The modems discussed above connect to an ordinary telephone line. A cable modem connects to the outside world through your cable TV line via a cable modem provided by your ISP, and to your computer via a network card, which goes inside the computer (see Network card, below). Cable modems are much faster than the fastest conventional modem, but also more expensive.

ADSL (Asymmetric Digital Subscriber Line): An ADSL connection looks like a connection using an ordinary phone line, but it uses an ADSL modem. A network card is also required to connect from your computer to the ADSL modem. It's several times faster than a cable modem connection.

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Network card, or Ethernet card, or NIC (Network Interface Card)

A modem and an ordinary telephone line is one way of connecting one computer to another, which is what you are doing when you access the internet and email. A network card will allow you to connect to other computers in your home or business, or the internet, web, etc. without a telephone line or modem (see What about cable modems?, above).

Network cards were designed from the beginning for direct (digital) connections between computers and the internet, and consequently can transfer data much faster than a modem or cable modem. There is some potential confusion here: if you have a cable modem, or an ADSL connection (see ADSL, above), you also need a network card.

What is the internet and world wide web, anyway? Simply put, it's millions of computers, all connected by various means. Any time you look at a web page, for example, you are looking at a file on another computer's hard drive. That computer might be across the room, or across town, or across the ocean. Everything you see on the web/internet is a file on some computer, somewhere. In fact, all the files that make up a given web page don't even have to be on the same computer. For more technical details, click here.

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Hardware and Software

Hardware is anything physical: the computer case and everything inside it (RAM, CPU, video card, etc.), the monitor, keyboard, mouse, printer, etc. - in other words, anything you can touch.

Software is programs and files of various types. You cannot touch them: they only exist as electrical signals, magnetic coatings on disk or tape, data encoded on CDs, or other media.

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Operating System, or OS

A car without a driver isn't going anywhere; likewise, a computer cannot do anything without an operating system. An operating system is a collection of programs that tell the machine how to run itself. Examples include DOS, Linux, OS/2, Unix, Windows, and many others you've never heard of, because they run things like microwave ovens and industrial machinery.

GUI vs. CLI

What's a GUI? All those pretty pictures, icons, and menus, as opposed to a command prompt, or command line interface (CLI). Any version of Windows earlier than 95 is not an operating system, but a graphical user interface (GUI = "gooey"), which ran on top of DOS (Disk Operating System, a type of CLI). In fact, the earliest releases of Windows 95 also ran on top of DOS. Later versions of Windows 95 (and all later versions of Windows) are an operating system and a GUI combined.

The GUIs that you see with Unix and Linux are not an essential part of the operating system (and I suspect the same is true of Macs), but run on top of, and in addition to, the OS. In other words, the GUI is just another program, and is therefore much less likely to crash the whole system. Windows has very limited functionality if all you can get from it is a command prompt, whereas many versions of Linux/Unix are fully functional operating systems, even with just a CLI. You can burn a DVD, watch a movie, or browse the internet (text only), and the mouse will work to an extent. Some server versions of Linux don't even install a GUI by default. They can be configured and managed with command prompt only, or remotely via a web interface.

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Copyright © Michael Ward 1999 - 2010