Desktop PC Terms
Motherboard
This is the board through which all the other components of the PC connect. Motherboards differ from each other depending on what "chipset" they use. The "chipset" is the brains of the motherboard. It performs all the custodial tasks of running a computer while the task of the CPU is to run your programs. Many motherboards now integrate peripheral devices such as video cards and modems. These motherboards are a good deal in initial cost, but in some cases those integrated peripherals cannot be later upgraded without buying a new motherboard as well.
Cache memory speeds up your computer by making the CPU wait less for memory requests. Most current PC CPUs put the cache on the CPU instead of the motherboard.
Choosing a Motherboard that supports a faster CPU than the one you start with provides an easy upgrade option.
I/O
Input/Output ports. This includes serial, parallel, external video and other connectors. The more types of ports you have, the more choices your computer has for communicating with other devices and computers. These are usually built-into the motherboard.
Ultra ATA (EIDE) is the current standard for mainstream hard drives. A high-speed COM port lets you use an external modem but is rarely used for anything else currently. The EPP port is a parallel port that can send data quickly to an attached printer. USB 2.0 is a new type of port that lets you put many different peripherals on one USB port. USB peripherals are becoming more common today, and USB support will soon be a necessity. Firewire (IEEE 1394) is a high-speed serial port similar to USB that many digital video devices and other high-speed peripherals require.
CPU
The CPU is the brain of the computer. Most of the time, your CPU is idle, so a faster CPU does not necessarily make a faster computer. However, some tasks, such as those involving multimedia presentations can require a great deal of CPU power.
Memory
Also known as RAM. This is where the computer's CPU works on problems. Having more RAM can give the largest increase in system speed, unless you already have enough, in which case adding more can be useless. How much is enough? Good question. Here are some guidelines for Windows XP:
| Light word processing, infrequent Web browsing, email, 1 open application at a time | 64MB |
|---|---|
| Moderate word processing, light Web browsing, spreadsheet, business graphics, more than 2 open applications at a time | 64-128MB |
| Complex word processing, page layout, illustration/graphics, multimedia Web browsing, complex spreadsheet, statistical applications, light CAD/Modeling | 128-256MB |
| Photo/Video editing, complex CAD/Modeling | 512MB+ |
Currently, there are dozens of different types of RAM. Make sure that you get RAM that is supported by your computer. If you're buying a system from a reputable vendor, this won't be a problem. The four main things to know about a memory part are:
- The technology used
- The physical layout
- The chip configuration
- The minimum access time
| Memory Technologies | ||
|---|---|---|
| Type | Abbreviation | Description |
| Fast-Page Mode | FPM | This is the oldest type currently sold. Only get this if you're motherboard does not support any other type. It is usually 5 volt. |
| Extended Data Output | EDO | On computer systems designed to support it, EDO memory allows a CPU to access memory 10 to 15 percent faster than comparable fast-page mode chips. EDO memory comes in 5 or 3.3 volt. If your motherboard supports it, use 3.3 volt. Never mix RAM of different voltages on the same motherboard. |
| Synchronous DRAM | SDRAM | These modules use little clocks to synchronize signal input and output on a memory chip. The clock is coordinated with the CPU clock so the timing of the memory chips and the timing of the CPU are in `synch.' Synchronous DRAM saves time in executing commands and transmitting data, thereby increasing the overall performance of the computer. SDRAM is almost always 3.3 volt. Never mix RAM of different voltages on the same motherboard. |
| Rambus | RDRAM | A newer memory technology struggling to gain acceptance, RDRAM is similar to SDRAM but moves data with fewer wires, theoretically giving it an advantage by allowing one to run many RDRAM chips in parallel. Currently the cost of RDRAM is prohibitive but dropping fast. 2.5 volt. |
| Double Data Rate Synchronous DRAM | DDRAM | An improvement to SDRAM that lets it transmit data twice as fast, putting it on par with RDRAM. Currently little support, but will soon be the technology of choice for mainstream computers and won't be more expensive than current SDRAM. 2.5 volt. |
| Physical Layouts | ||
|---|---|---|
| Type | Abbreviation | Description |
| Single In-Line Memory Module | SIMM | The 72 pins of this package allow for 16-bit access. Pentium class motherboards access memory in 32 bit words, so you have to use this type of module in pairs. 30 pin SIMMs also exist, but are not used on current motherboards. |
| Dual In-Line Memory Module | DIMM | The 168 or 184 pins of this package allow for 32-bit access. You can therefore install these modules individually on a Pentium class motherboard. These packages are notched slightly differently for 3.3v, 5v, and buffered/unbuffered so that you can't install the wrong type of memory on your motherboard. |
| Rambus In-Line Memory Module | RIMM | 184 pin package for RDRAM only. 2.5v. |
| Laptop Memory | N/A | Unfortunately, laptop memory is even less standard than desktop. Some laptops use SIMMs, some DIMMs, and many use proprietary memory cards. In general, never buy a laptop memory module that does not explicitly state that it is for the model or series of your laptop. |
| Chip Configurations | ||
|---|---|---|
| Type | Abbreviation | Description |
| Non-Parity | N/A | Also known as standard. This configuration has just enough chips to do the job. |
| Parity | N/A | This configuration has one extra bit per word. If this bit does not add up correctly, a parity error has occurred and the system is halted to prevent data corruption. |
| Error Correcting | ECC | This configuration has enough extra bits per word that if a single bit is incorrect, the motherboard can figure out which one is wrong and correct it. This is the most robust type of the three here. Many motherboards can link together two parity SIMMs and end up with enough extra bits to treat them as a single ECC unit. |
| Memory Access Times |
|---|
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For EDO and FPM memories, the minimum access time is expressed in nanoseconds. Lower is better. This number is just a rating, putting faster RAM in your computer will not speed it up, but it may let you tell the computer to try and access its RAM faster, which will speed the computer up. Accessing RAM beyond its rated capacity can cause slowdowns and errors. |
|
For SDRAM, the minimum access time is either express in nanoseconds or in MHz. The MHz rating is the fastest clock speed to which the memory module can sync itself. The MHz rating is frequently give as PCxxx where xxx is the MHz rating. The nanosecond rating is the period of one of these clock cycles. E.g. PC100 is usually equivalent to 10ns, 83Mhz is usually equivalent to 12ns. Memory with a faster than needed speed rating can be used at a slower rate without problem. Therefore it would be wise to get the fastest rated memory you can find for future compatibility. |
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RDRAM is labled with the memory bus speed, like SDRAM, but multiplied by 2 since RDRAM can transfer 2 units of information per clock cycle. An example would be PC800. This is not comparable to SDRAM labling since the memory types transfer memory very differently. A PC800 RDRAM is about as fast as as a PC133 SDRAM in most applications. Some high-end systems can use multiple channels of RDRAM at the same time. For example, the i840 chipset supports 2 channes at the same time. This nearly doubles the memory performance. |
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DDRAM is labled with its peak memory bandwidth, e.g. PC1600 means 1.6GB/sec. Again, this is not comparable to other labling types. A PC2100 DDRAM channel is generaly about as fast as PC250 SDRAM or a dual-channel PC800 RDRAM system. PC2700DDR is more commonly caled DDR333, refering to its clock speed x2. |
Case, Power Supply
There are 4 main choices in case styles: Desktop, Mini-Tower, Mid-Tower, and Tower.
Desktops are designed be on a desk, with the monitor on top of the case. This usually places the monitor too high, however, and does not allow for proper cooling of the CPU. Mini-Towers are designed to be the smallest enclosure that can hold all your components, and be placed out of the way. Mid-Towers are designed for expansion, and for those that like a little more presence from their computer. Tower or Full-Tower cases are for servers where many hard drives and other components need be placed inside the case, or for those who require a looming presence from their computer.
For a typical system, 300 Watt power handling is adequate, more is better. Use power supply recommended by AMD or Intel as appropriate.
Hard Drive
Also known as storage. This is where the computer puts programs and information for permanent storage. Always buy as much as possible. The trend in software has been toward larger and larger application suites, so a good rule of thumb would be to think of the largest amount of storage you will need, then double that. Though on most systems, you can always add a second hard drive later if need be.
A faster hard drive can speed up many tasks on your computer. In general, hard drives that spin at a faster RPM rate are faster overall. The other main factor in a hard drive's speed is the time it takes to find a given piece of data, also known as "access time". A hard drive with a lower access time will usually be faster.
Removable Storage
3.5" 1.44MB is standard. Floppy disks are used for backups, transfers between computers, and software distribution. They should never be used as primary storage as they have failure rates hundreds of times higher than hard drives.
Zip Drives are another removable media drive. They perform the same function as floppy drives, but the disks can hold about 70 times more information. Their failure rate is much better than floppy drives as well, but they are still less reliable than a hard drive, so they too should not be used as primary storage.
CD-RW drives can function like floppy drives in most systems. In addition, the disks written with CD-RW can be read in most newer CD and DVD drives. They hold about 450 times more than a floppy when used as a backup device, and about 350 times more when used in the same manner as a floppy drive. Their failure rate is highly dependent on thier physical condition and care.
DVD+RW and DVD-RW are competing standards for rewritable DVD media. Both format's write-once media (DVD+R and DVD-R respectively) are generally compatible wtih older DVD readers, but they are not compatible with each other. At the time of this writing, DVD+R media was cheaper and more readily available. Many DVD writers can also read and write CD-R and/or CD-RW.
Optical Drive
This is necessary for loading many software titles, and can usually be used as an audio CD player as well. The x rating (e.g. 12x) is a measure of how fast the CD spins compared to an audio CD player.
New CD-ROM drives are starting to use constant angular velocity mechanisms (audio and older computer mechanisms are constant linear velocity). Therefore the data can be read faster at the edges of the disk as compared to the inner tracks. These newer drives will give either give a speed rating at the inner and outer tracks (e.g. 12-24x) or will give the outer track speed only (e.g. 20x Max). However, there is no standards body for CD-ROM drive naming, and several manufacturers add a few to the x rating. Access time and transfer rate are the most important aspects of CD-ROM drive. Lower is better for access time, higher is better for transfer rate.
Monitor
This is your primary feedback from the computer. Larger monitors are easier to read, and higher resolution monitors give you more places to put your multiple windows.
Most monitors are listed similar to this: 17" 1280x1024 .26mm
The first number is the diagonal tube size; the viewable size will be about an inch less than this.
The second number is the highest resolution that can be viewed at 60Hz vertical refresh. 60Hz vertical refresh is the same as a TV, but long term close viewing at this refresh rate bothers many people. It's a good idea to get a monitor rated one resolution bracket above where you really want so that you can view your chosen resolution at 72Hz or greater, the ergonomic standard for monitor refresh rates set by VESA. The resolution brackets are:
1600x1200
1280x1024
1024x768
800x600
640x480
The manufacturer might list a vertical refresh rate such as 1280x1024@72Hz instead, which would be fine for 1280x1024. Another thing to remember about resolution is that it's impractical to view higher than 1024x768 on a 15" monitor or 1280x1024 on a 17" monitor unless you put your nose 2" from the screen.
The last number is dot pitch and is a rough indicator of the quality of the tube. This number is the spacing between individual phosphors of the same color on the surface of the tube. Lower spacing is better, as small details will show better. .28 dot pitch is about the largest one should go on a standard mask monitor. For Trinitron or stripe mask screens, .26mm is the largest one should go since the stripes are rectangular and the measurement quoted is across the short side of the rectangle.
A new type of monitor that you might consider is the flat panel display. This is essentially a laptop monitor that has been put into a stand-alone case for use with desktop systems.
Advantages to this type of display are:
- Much lighter
- Much thinner
- "Digital" models have very sharp images, esp. with text
- No flicker
Disadvantages are:
- Higher cost per screen size (though this is falling)
- "Digital" models require special video card
- Only one built-in resolution. Other resolutions look odd.
- May be a few "stuck" pixels, just like a laptop
Video Card
The video card can play a large role in the performance of your system. If you're looking for a good card, the two most important factors are chipset and amount of RAM.
The chipset of the video card is the card's brains. There are many out there and they all perform differently. It's best to look for at least a 64bit processor and some multimedia extensions built in to the card. The chipset of a video card is more critical for game applications than business applications.
The amount of RAM determines how large an image you can display at a given color depth. 4MB is a common configuration, but for 3D effects, 8 MB or more would be useful.
You can usually look on the box of a video card to find out what combinations of video resolution, colors, and refresh rates it supports.
Keyboard
The keyboard, like the case and the mouse is a matter of personal preference. If possible, try out any prospective purchase first, or at least a very similar setup.
Sound Card
Sound Blaster compatibility is important if you wish to play games. For Windows system sounds or multimedia, any 16-bit audio card will do. For musical composition, a general MIDI (GM) wave table synthesis card is a must. Newer systems should use PCI based sound cards. Newer games are taking advantage of 3D audio effects, which are aided by cards with 3D audio support.
Speakers
This is a matter of preference. Powered speakers tend to sound better than those driven by the sound card's amplifier. Three-speaker systems with a subwoofer tend to sound better than two-speaker systems.
Mouse
The mouse, like the case and the keyboard, is a matter of personal preference. If possible, try out any proposed purchase first, or at least a very similar setup. MS Mouse compatibility is a plus.
Operating System
This is the program that runs all the other programs you use. Windows operating systems have recently started to include many common applications as well.
Ethernet Card
If you connect through an Ethernet port, this is a must have item.
Modem
This provides network connectivity over the phone. 53/33.6 thousand bits per second (v.92 download/upload) is the fastest speed currently available.
Many modem alternatives are emerging. These include ISDN, xDSL, and cable modems. These new technologies are all faster and generally more expensive than a traditional modem. Contact your local phone company or cable provider to see if they are offered in your area.
Warranty
One year is standard. More is better.
