Designing and Building (or Buying) a Personal Computer

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Designing and Building (or Buying) a Personal Computer

New postby Bud » Sat Dec 24, 2005 4:03 pm

Preliminary Decisions:

So, you want to build a new PC. It's not very difficult if you're reasonably adept. However, it may or may not be worth the effort depending on what you want. The first step in building a new computer system is deciding what you want to do with it. After you've figured that out, you can make the build-or-buy decision.

1. What do I want to do with the computer?

Once upon a time, buying a new computer meant buying one with the fastest CPU you could get (measured in mega-Herts, MHz). However, things have changed (in reality, it was never quite that simple). Now days, choosing a computer is a lot like choosing an automobile. You wouldn't buy a Corvette to take the socker-team to practice and you wouldn't buy a minivan to haul a 5th-wheel trailor.

For a computer, this decision equates to deciding what software you're going to run on it. The ONLY reason to buy (or build) a computer is because there is software you want to use on it. Without software, a computer is just a space heater and an overly expensive, not very efficient one at that.

You don't necessarily have to know exactly what programs you will use, but you should know what types of programs you want to use. Different classes of programs will make different demands on the computer and help determine what features are important to you. For example:

Personal Assistant:

Most modern PCs can run software such as personal accounting, word processing, tax accounting, and similar office programs. These programs do not normally require high-performance or special peripherals other then a printer.


In order for a computer to send or receive E-mail or browse the Internet, it will need an Internet connection. The most important thing I can say here is that dial-up sucks. Find out what "broadband" services are available in your area (either cable or DSL) and get it. Web and E-mail programs don't place any special performance demands on the system so the only special hardware you'll need is the modem or network connection.


The personal computer is starting to become a very useful tool for managing and manipulating your personal media collections (audio and video). Most modern PCs can manage large audio collections with ease, although you may want to be sure you have a high-quality audio CODEC and speakers depending on how you plan to play back your music. Video, on the other hand is a different story. Managing large video files requires massive amounts of storage space. Editing video, requires very high performance (possibly a special hardware accelerator card). And, capturing video requires special hardware or a DVR (Digitial Video Recorder, like TiVo) connected to your computer via a network.


Gaming is the big performance hog. The latest and coolest games always require the latest and coolest computer hardware. CPU performance and memory are important. Graphics performance is even more important. Many good games these days also allow you to interact with people on the Internet and you'll need a broadband link for this as well.

The Operating System:

One special piece of software that (almost) every computer has is called the Operating System (OS). To use the automotive analogy again, if the CPU is the engine of the computer, then the OS is the traffic cop (and rules of the road). The engine does you no good if you've ran into a tree. In order for all the other software to do anything useful, it must follow the rules of the operating system. And just like you woudln't drive on the left-hand side of the road in the USA, you wouldn't use the software from one operating system on a computer running another.

Fortunately (or unfortunately, depending on your personal beliefs), Microsoft Windows (and it's variants) are ubiquitous and most of the software you're likely to want runs on it. I recommend Windows XP (I like the professional version, but it's expensive and the personal version is fine). The second largest competitor is probably Linux. If you choose Linux (which is great if the software you want to use runs on it), I recommend buying a professional distribution. Red Hat is more common, but I like the SuSe distribution better.

2. Should I build it or buy one?

Now that you've thought a little bit about how you want to use your computer, you can make a decision as to whether or not to build your own or buy one. It used to be the case that you could build one cheaper then you could buy a PC pre-made. Now days, a medium-to-low performance PC is cheaper to buy then build and it will save you a lot of trouble.

However, if your desired usage hit one of the cases I mentioned above that requires special hardware, you may be better off building your own or modifying one after you buy it. Computer makers charge a premium for large storage capacity (hard disk drive, HDD), the latest and greatest CPU, and for special peripherals like high-end graphics cards and video capture boards. I recommend you buy them yourself and install them if you're at all capable of it.

(Continued... Basic PC architecture, next.)
Last edited by Bud on Sun Dec 25, 2005 12:42 pm, edited 1 time in total.

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Basic PC Architecture

New postby Bud » Sat Dec 24, 2005 4:56 pm

Before you attempt to build (or buy, for that matter) a PC, you should know a little bit about what a PC is. The following is a simplified diagram of the main logical blocks of a PC.



The motherboard is the large central circuit board of the computer. The other blocks are either built into the "motherboard" (inside the dashed box) or plug into the motherboard (outside the dashed box).


The CPU (Central Processing Unit), is the "brain" of the computer. This is the part that "runs" all the programs (including the OS). It is also the part that most people have heard of.


The hub (also called the Northbridge or Interconnect Controller Hub - ICH) is basically a high-speed switching system that allows the CPU to talk to the other parts of the computer at the fastest rate that it can.


The video subsystem is what allows the computer to display text and images on a monitor. This can be very simple, supporting only text and 2D graphics or it can be highly complex and expensive, supporting high-speed 3D graphics and possibly motion-picture decoding.


This is the computer's short-term (or volatile) memory. In order for the CPU to run a program, it has to be (at least partially) held in this memory. RAM means Random Access Memory, an old term that has survived from the early days of computing that means any portion of the memory can be accessed directly without having to look through all the other parts that come "before" the desired part. The important thing to know about RAM is that it is volatile, meaning it looses anything stored in it when the computer's power is turned off. This requires programs and data to be saved in secondary storage, on the Hard Disk Drive (HDD), if you want to keep them.


The IO (Input-Output) bridge (sometimes called the "Southbridge" or "super IO" chip) is really a collection of many different interconnections that used to be separate devices on older computers. This includes connections to most of the peripheral devices that the computer uses, such as the keyboard, mouse, serial and parallel ports, hard-disk, audio CODEC connections, USB etc.


A bus is a collection of wires and the mechanical, electrical, and protocal (rules) that that allow one electronic device to communicate with another. Busses are how these complicated devices are connected together and in order for any two devices to communicate they must support a common bus.

Front-Side Bus (FSB)

The bus that connects the CPU to the rest of the system is called the "front-side" bus. This is usually different for different families of CPUs. When you build a computer system, you have to be careful to make sure that the FSB of the CPU is supported by the "socket" of the motherboard that it plugs into.

System Bus

The system bus is the central "expansion" bus that the motherboard provides to allow new hardward devices to be connected to the computer system that were not built into it and do not have a dedicated peripheral connection (such as a keyboard). In modern systems this is usually a PCI (Peripheral Component Interconnect) bus, although other busses have been used in the past (and will be used in the future).

Video Bus

In older systems, the video (or graphics) card (circuit board containing the video subsystem) was plugged directly into the system bus. However, modern graphics cards require so much data at a very high rate and modern systems have seperated this onto a seperate bus because the standard system busses were not fast enough for the work load. There are currently two common video busses, AGP (Advanced Graphics Port, the older bus) and PCI-X (PCI Express, the newer technology).

Memory Bus

The memory bus is how the memory is connected to the hub. It is rarely discussed seperately from the memory itself. When the documentation for a motherboard says it supports a particularly type of memory (ex PC-3200 SDRAM), that means it has the memory bus for that type of memory. You must buy the type of memory that is supported by your motherboard. This may effect your decision on which motherboard you buy.

Peripheral Interconnects

Common peripheral devices have dedicated connections to the computer. The documentation for a motherboard will generally list the peropherals it supports. Most motherboards these days support a keyboard and mouse (PS2-style), several USB (Universal Serial Bus) ports, hard disk drive ports (ATA-or-IDE is the older style, Serial-ATA/SATA is the newer one). Many also support a network connection (Ethernet), audio, and other devices. Make sure the motherboard you choose supports the devices you want.

Continued... choosing the parts to put together, next.
Last edited by Bud on Mon Jan 02, 2006 5:35 pm, edited 1 time in total.

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Key Peripherals & a Little Religion

New postby Bud » Sun Dec 25, 2005 2:48 pm

The above architecture description focused on the main "internal" parts of the computer. There are a few key peripherals (some internal and some external) that are critical to any computer system.

Hard Disk

We discussed computer memory (RAM) earlier and mentioned that it was volatile. In order for a computer to store programs and data, it must have a hard disk (or some other form of "secondary storage") that maintains its contents after the power is turned off. Modern operating systems also use the HDD (Hard Disk Drive) to swap large programs and data from the main memory to make it appear that the computer has more RAM then it really does. The important features of the HDD are size (get at least 40 GB - Giga Bytes or more), the access speed (measured in some small number of milliseconds) and the data throughput (measured in MB/s - Mega Bytes per second).


In order for the use to see the output visual output (text or graphics) from a program (and the OS) it has to have a monitor. LCD monitors have become very affordable and personally, I like the image they provide better then a CRT (Cathode Ray Tube, like an old fashioned TV). I also like a wide screen, especially if you're going to do gaming or watching videos.

Keyboard & Mouse

A modern computer nees both of these vital input devices, but they're generally pretty boring. Pick the ones you like. You'll pay more for wireless technology, but it's worth it if you have the need.


Audio consists of more then just speakers, but they're the main element. Most motherboards have the audio CODEC (encoder-decoder) to convert the audio from analog to digital and vice versa. Just make sure your motherboard satisfies your need or buy a seperat audio card that does. Speaker choice depends on what you're doing with the PC.


A pretty simple issue... if you need printed output, you need a printer. If you want color you'll pay more. Ink-jet printers provide a nice quality output, but if you only print a few pages every other month, they'll dry out and you need to buy new expensive ink cartridges. Laser printers will cost more up front, but the ink doesn't dry out (rather it's dry to begin with).


If you have a computer, you should be connected to the Internet for E-mail and online research. You'll need the modem (modulator-demodulator) that is required by your connection type. If you have several computers at home, a network hub (or wireless access point) will allow them to share a single Internet link, but each PC will need a network card (wired or wireless, depending on the hub/access point type). I recommend going with the 802.11G wireless standard (50+ MB/s data rate) or the 10/100T Ethernet, wired network standard (100 MB/s,w/backwards compatiblity to 10MB/s cards).

All of these peripherals connect to the IO bridge or to connections that connect through them unless they are on cards that plug directly into the system bus.

Religious wars

I feel obligated to point out that processor and operating system choice is something or a religious war. Some people prefer Intel processors, others prefer AMD. Many people use Microsoft Windows, but there's an entire community of people who use and support Linux. There are other players in both of these areas, but these are the big ones. In the interest of full disclosure, I am an Intel purist and OS agnostic (although I primarily use Windows because it runs the software I use most).

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Selecting the components

New postby Bud » Mon Jan 02, 2006 6:16 pm

The good news is that you don't have to have a degree in computer engineering to figure out what you need (although it does help). :wink: Once you understand the basic architecture of a PC, the problem is reduced primarily to a task of choosing the components that fit your need and making sure that they support the same connection standards (electrical, mechanical, and/or logical).

Fortunately, the busses and connections are all standardized. So, you don't have to worry about the details of how a bus works. All you have to do is match the standard. As long as the parts that connect toghether use the same bus or connection standard, they should work correctly. You may need to be careful of variations of a particular standard. Some standards have speed or voltage variations. Many times they are backward compatible, but if you connect a part that supports a newer standard to a part the only supports the older variant, you will loose the benefit of the updated standard.

So, what parts do you need? From the diagram above you can figure out the important stuff. Everything else falls into the category of things needed to make the important stuff work or peripherals. Here's a quick checklist.

Parts Checklist:
    Computer Parts Checklist
    Video Card
    Hard Disk Drive(s)
    CD/DVD ROM Drive
    Floppy Drive (if any)
    Power Supply

That's the basic list. You may need a few cables (especially for the disk drives), but the case will usually come with most of the mechanical connectors needed. Other then that, things fall into the peripheral category.

to be updated later

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