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13 décembre 2010 1 13 /12 /décembre /2010 02:49

desktop computer is a personal computer (PC) in a form intended for regular use at a single location, as opposed to a mobile laptop or portable computer. Prior to the widespread use of microprocessors, a computer that could fit on a desk was considered remarkably small    (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

Desktop computers come in a variety of types ranging from large vertical tower cases to small form factor models that can be tucked behind an LCD monitor. "Desktop" can also indicate a horizontally-oriented computer case usually intended to have the display screen placed on top to save space on the desktop    (Dell Studio XPS 1340 Battery)    .

Most modern desktop computers have separate screens and keyboards. Tower cases are desktop cases in the earlier sense, though not in the latter. Cases intended for home theater PC systems are usually considered to be desktop cases in both senses, regardless of orientation and placement     (Dell Studio XPS 1640 Battery)   .

History

Early computers took the space of a room. Minicomputers generally fit into one or a few refrigerator sized racks. It was not until the 1970s when computers such as the HP 9800 series desktop computers were fully programmable computers that fit entirely on top of a desk    (Dell Vostro 1710 Battery)      .

The first large calculators were introduced in 1971, leading to a model programmable in BASIC in 1972. They used a smaller version of a minicomputer design based on ROM memory and had small one-line LED alphanumeric displays. They could draw computer graphics with a plotter       (Sony VGP-BPS13 battery)      .

The Wang 2200 of 1973 had a full-size CRT and cassette tape storage. The IBM 5100 in 1975 had a small CRT display and could be programmed in BASIC and APL. These were generally expensive specialized computers sold for business or scientific uses. By the late 1970s and 1980s personal computers such as the Apple II series and the IBM Personal Computer used standard processors to reduce cost to put a complete computer on top of a desk with a separate monitor     (Sony VGP-BPS13/B battery)    .

These would find uses in the home as well as in business and industry, and later incorporate graphic user interfaces and powerful networked operating systems such as Mac (Macintosh) and Windows    (Sony VGP-BPS13/S battery)     .

All-in-one

All-in-One computers are desktop computers that combine the monitor into the same case as the CPU. Apple has manufactured several popular examples of all-in-one computers, such as the original Macintosh of the mid-1980s and the iMac of the late 1990s and 2000s     (Sony VGP-BPS13A/B battery)        .

Some older 8-bit computers, such as the Commodore PET 2001 or Kaypro II, also fit into this category. All-in-One PCs are typically more portable than other desktop PCs and many have been built with carrying handles integrated into the case. They can simply be unplugged and transported to a new location      (Sony VGP-BPS13B/B battery)      .

Like laptops, All-in-One desktop computers are characterized by a comparative lack of upgradeability or hardware customization, as internal hardware is often placed in the back of the visual display unit. Furthermore, in the case of the iMac line since 2002, the CPU and other internal hardware units are, more or less, permanently glued to the motherboard due to space constraints  (Sony VGP-BPL9 battery)      .

However, latest models of the All In One Computer have changed their approach to this issue. Many of the current offerings, like the Handii myFace and others, are using standard off-the-shelf components and are designing upgrade convenience into their products (Sony VGP-BPS13B/B battery)     .

Comparison with laptops

Desktops have the advantage over laptops that the spare parts and extensions tend to be standardized, resulting in lower prices and greater availability. For example, the form factor of the motherboardis standardized, like the ATX form factor   (Sony VGP-BPS13B/B battery)   .

Desktops have several standardized expansion slots, like Conventional PCI or PCI express, while laptops only tend to have one mini PCI slot and one PC cardslot (or ExpressCard slot). This means that a desktop can be customized and upgraded to a greater extent than laptops     (Sony VGP-BPL11 battery)   .

Procedures for (dis-)assembly of desktops tend to be simple and standardized to a great extent too. This tends not to be the case for laptops, though adding or replacing some parts, like the optical drive, hard disk, and adding an extra memory module is often quite simple   (Sony VGP-BPL15 battery)        .

Another advantage of desktop is, that (apart from environmental concerns) power consumption is not as critical as in laptop computers because the desktop is powered from the wall socket. Desktop computers also provides more space for heat to escape. The two large microprocessor manufacturers Intel and AMD develop special CPUs for mobile computers (i.e. laptops) that consume less powerand lower heat, but with lower performance levels     (Dell Inspiron E1505 battery)   .

On the other hand, laptop computers offer portability that desktop systems can not due to their small form factor. Laptops also more commonly integrate wireless technologies like WiFi, Bluetooth and3G, giving them a broader range of options for connecting to the internet, though this trend is changing as more desktop computers come integrated with wireless     (Dell Latitude E6400 battery) .

Operating systems

An operating system is the program that after being initially loaded into the computer by a boot program, manages all the other programs in a computer   (HP Pavilion dv6000 Battery)     .

Most of today's desktop computers have one of the three major operating systems available. In order of usage share, they are Microsoft Windows, Mac OS X, and Linux. Microsoft Windows and Linuxcan be used for almost any desktop computer, although Mac OS X can be used on some computers that aren't Apple branded, the legality of this is currently disputed  (Sony Vaio VGN-FZ31S battery)     .

Mac OS has been designed by Apple to only work on Apple computers unless you have an EFI emulator which creates an environment that can boot Mac OS X on a regular PC. New versions of each of these operating systems are released on a semi-regular basis     (Sony VGN-FZ31S battery)    .

The newest version of Microsoft Windows is called Windows 7 and is widely regarded as a marked improvement over the previous Windows Vista. The newest version of Mac OS is Mac OS X Snow Leopard. Linux is available in multiple distributions, the more popular being Ubuntu, Fedora and openSUSE. Each distribution has its own version number and bundled software, but all distributions of Linux contain a Linux kernel   (SONY VGN-FZ38M Battery)     .

Average selling price

For Microsoft Windows systems, the average selling price (ASP) showed a decline in 2008/2009, possibly due to low-cost Netbooks, drawing $569 at U.S. retail in August 2008. In 2009, ASP had further fallen to $533 by January. All in one Mac desktops such as the 21.5 inch iMac start at $1,199. All in one PC's running Windows start at $399    (SONY VGN-FZ31z Battery)  .

Gaming computer

gaming computer (also gaming PCgaming machine and gaming rig) is a personal computer that is capable of playing computationally demanding video games. Gaming computers are very similar to conventional PCs, with the main difference being the addition of a performance-oriented video card    (Sony VGN-FZ31Z Battery)      .

Gaming computers are often associated with enthusiast computing due to an overlap in interests. However, while a gaming PC is built to achieve performance for actual gameplay, enthusiast PCs are built to maximize performance, using games as a benchmark. The difference between the two carries a large discrepancy in the cost of the system     (SONY VAIO VGN-FZ38M Battery)       .

Whereas enthusiast PCs are high-end by definition, gaming PCs can be subdivided into low-end, mid-range, and high-end segments. Contrary to the popular misconception that PC gaming is inextricably tied to high-priced enthusiast computing, video card manufacturers earn the bulk of their revenue from their low-end and mid-range offerings     (SONY VGN-FZ31E Battery)    .

Because of the large variety of parts that can go into a computer built to play video games, gaming computers are typically custom-made, rather than pre-assembled, either by gaming and hardware enthusiasts or by companies such as Alienware, Falcon Northwest, VoodooPC, LanSlide Gaming PCs and Origin PCthat specialize in producing custom gaming machines     (SONY  VGN-FZ31J Battery)   .

In order to generate interest, gaming computer manufacturers that sell complete systems often produce boutique models, allowing them to compete on aesthetic design in addition to the hardware inside.

Hardware

Historically, gaming computers had several distinct hardware components that set them apart from a typical PC    (SONY VGN-FZ31M Battery)     .

The push for better graphics began with color fidelity, from display systems such asCGA eventually graduating to VGA, which was adopted for the mass market. Gaming also led the push for the adoption of sound cards, a component that is now commonly integrated ontomotherboards    (SONY VGN-FZ31B Battery)    .

In the 1980s, several non-IBM PC compatible platforms gained a measure of popularity due to advanced graphics and sound capabilities, most notably the Commodore 64 and Amiga. Computer game developers of the time targeted these platforms for their games, though typically they would later port their games to the more common PC and sometimes Apple platforms as well  (SONY VGP-BPS13 Battery)       .

The MSX was also popular in Japan, where it preceded the video game console revolution.

LAN parties helped to promote the use of network cards and routers. This equipment is now commonly used by non-gamers with broadband Internet access to share the connection with multiple computers in the home  (Dell Inspiron 1320 Battery)  .

Like sound cards, network adapters are now commonly integrated on motherboards.

In modern times, the primary difference between a gaming computer and a typical PC is the inclusion of a performance-oriented video card, which hosts a graphics processor. Some motherboards support up to four video cards through SLI or Crossfire (Dell Inspiron 1320n Battery)     .

However, such configurations are typically regarded as a curiosity for enthusiasts rather than a useful alternative to single-card upgrade cycles.

Forays into physics processing have also been made, though with Nvidia's buyout of PhysX and Intel's buyout of Havok, plans are that this functionality will be combined with existing CPU or GPU technologies     (Dell Inspiron 1464 Battery)  .

Prebuilt Gaming PC

While many "hardcore" gamers build their gaming PCs themselves, some choose to go with prebuilt or custom-built gaming PCs. These PCs can often be more expensive than building one's own, with higher premiums attached to high-end brands with varying levels of customer service     (Dell Inspiron 1564 Battery)    .

Different companies offer varying degrees of customization, some almost as much as building it oneself. There are however, drawbacks to building one's own computer. Assembling a computer means being personally responsible for any problems that may arise, both during the assembly phase, and after it's in regular use       (Dell Inspiron 1764 Battery)    .

Instead of using a single technical support hotline to cover your entire system, often one will have to deal with individual component manufactures. Due to the wide inconsistencies in after purchase support from component manufactures, trying to get support can be a daunting task for even the most patient of persons     (Dell Studio 1450 Battery)     .

Customer support is a major reason why even extreme gaming enthusiasts may look to a system integrator for their custom PC builds. There are many positive aspects in choosing to build one's own system, such as no longer being tied to specific configurations. Pricing on individual components is often better, and thus saves quite a lot of money on a comparable pre-built system    (Dell Studio 1457 Battery)     .

Gaming laptop

Gaming laptops are the mobile equivalent of gaming desktops and are usually more expensive than their desktop counterparts. Currently, most gaming laptops feature more power efficient versions of high end desktop graphics cards, which still drain heavily on battery life, and necessitate more advanced cooling systems      (Dell Latitude D610 Battery)      .

One recent development by NVIDIA is SLI for laptops. Generally, gaming laptops are not considered "rigs" as the term can also refer to the physical size of the system. Modern gaming laptops can achieve respectable game performance, but never quite match desktops in a class to class comparison, and most do not feature upgradeable graphics cards     (Toshiba NB100 Battery)     .

Due to the relatively small size that the hardware has to fit in, cooling the heat intensive components is a major problem affecting the performance of such laptops, usually causing degraded value for money performance wise. Attempts at using the same performance hardware as desktops usually end in a decreased clock frequency of graphics chips to reduce heat, causing the poor value for money (Toshiba Satellite M65 battery)  .

A newer trend in the gaming PC industry is to create small form factor desktops that are easy to transport. Several companies provide lines that specialize in these computers     (Toshiba Satellite M60 battery)       .

Public computer

public computer (or public access computer) is any of various computers available in public areas. Some places where public computers may be available are libraries, schools, or facilities run by government      (Dell Latitude D830 Battery) .

Public computers share similar hardware and software components to personal computers, however, the role and function of a public access computer is entirely different. A public access computer is used by many different untrusted individuals throughout the course of the day      (Dell Latitude D620 Battery)      .

The computer must be locked down and secure against both intentional and unintentional abuse. Users typically don't have authority to install software or change settings. A personal computer, in contrast, is typically used by a single responsible user, who can customize the machine's behavior to their preferences    (Dell Inspiron Mini 10 Battery)     .

Public access computers are often provided with tools such as a PC reservation system to regulate access.

The world's first public access computer center was the Marin Computer Center in California, co-founded by David and Annie Fox in 1977      (Sony VGN-FW11S Battery)

Public computers in the United States

Library computers

In the United States and Canada, almost all public libraries have computers available for the use of patrons, though some libraries will keep users timed to allow others to get turns and keep the library less busy      (Sony VGN-FW11M Battery)   .

Users are often allowed to print documents that they have created using these computers, though sometimes for a small fee. When using these computers, it is a smart idea to bring a USB flash drive for digital note-taking or bringing files home if the need arises (Sony VGN-FW139E/H battery) .

School computers

The U.S. government has given money to many school boards to purchase computers for educational applications. There is usually Internet access on these machines, but some schools will put up a blocking service to limit the websites that students are able to access to only include educational resources, such as Wikipedia or Google     (Dell Latitude E5400 Battery)   .

In addition to controlling the content students are viewing, putting up these blocks can also help to keep the computers safe by preventing students from downloading malware and other threats. However, the effectiveness of such content filtering systems is questionable since it can easily be circumvented by using proxy websites, Virtual Private Networks and for some weak security systems merely knowing the IP address of the intended website is enough to go through    (Dell Latitude E4200 Battery)   .

Computer case

computer case (also known as a computer chassiscabinetboxtowerenclosurehousingsystem unit or simply case) is the enclosure that contains most of the components of a computer (usually excluding the display, keyboard and mouse)     (Dell Vostro A840 Battery)      .

A computer case is sometimes incorrectly referred tometonymously as a CPU or hard drive referring to components housed within the case. CPU was a more common term in the earlier days of home computers, when peripherals other than the motherboard were usually housed in their own separate cases       (Dell Inspiron 300M Battery)     .

Cases are usually constructed from steel (often SECC—Steel, Electrically Chromate Coated) or aluminium. Plastic is sometimes used, and other materials such as wood and even Lego blocks have appeared in home-built cases.

Sizes

Further information: Comparison of computer form factors (Dell Studio 1737 battery)

Cases can come in many different sizes (known as form factors). The size and shape of a computer case is usually determined by the form factor of the motherboard, since it is the largest component of most computers. Consequently, personal computer form factors typically specify only the internal dimensions and layout of the case    (Dell Inspiron E1505 battery)      .

Form factors for rack-mounted and blade servers may include precise external dimensions as well, since these cases must themselves fit in specific enclosures.

For example, a case designed for an ATX motherboard and power supply may take on several external forms, such as a vertical tower (designed to sit on the floor, height > width) or a flat desktop(height < width) or pizza box (height ? 2 inches, designed to sit on the desk under the computer's monitor)      (Dell RM791 battery)     .

Full-size tower cases are typically larger in volume than desktop cases, with more room fordrive bays and expansion slots. Desktop cases—and mini-tower cases designed for the reduced microATX form factor—are popular in business environments where space is at a premium     (Dell XPS M1530 battery)      .

Currently, the most popular form factor for desktop computers is ATX, although microATX and small form factors have also become very popular for a variety of uses. Companies like In Win Development, Shuttle Inc. and AOpen have popularized small cases, for which FlexATX is the most common motherboard size    (Dell XPS M2010 battery)    .

Apple Inc. has also produced the Mac Mini computer, which is similar in size to a standard CD-ROM drive   .

Tower cases come in mini-tower, mid-tower, and big-tower/full-tower sizes. Full tower cases are typically 22 inches or more in height and intended to stand on the floor       (Dell Vostro 1000 battery)     .

They have anywhere from six to ten externally accessible drive bays, with more bays only internally accessible. The ratio of external to internal bays is shifting, however, as computing technology moves from floppy disks and CD-ROMs to large capacity hard drives, USB flash drives, and network-based solutions      (Acer Aspire One battery)     .

Midtower cases are smaller, about 18" high with two to four external bays. A minitower case will typically have only one or two external bays and stand from 14" to 16" tall.

Layout

Computer cases usually include sheet metal enclosures for a power supply unit and drive bays, as well as a rear panel that can accommodate peripheral connectors protruding from the motherboard and expansion slots     (Toshiba Satellite P10 Battery)   .

Most cases also have a power button or switch, a reset button, and LEDs to indicate power status as well as hard drive and network activity. Some cases include built-in I/O ports (such as USB and headphone ports) on the front of the case. Such a case will also include the wires needed to connect these ports, switches and indicators to the motherboard        (SONY VGN-FZ210CE Battery)   .

Major component locations

  • The motherboard is usually screwed to the case along its largest face, which could be the bottom or the side of the case depending on the form factor and orientation     (Dell Precision M70 Battery)     .
  • Form factors such as ATX provide a back panel with cut-out holes to expose I/O ports provided by integrated peripherals, as well as expansion slots which may optionally expose additional ports provided by expansion cards.
  • The power supply unit is often housed at the top rear of the case; it is usually attached with four screws to support its weight (Toshiba Satellite L305 Battery)   .
  • Most cases include drive bays on the front of the case; a typical ATX case includes both 5.25" and 3.5" bays. In modern computers, the former are used mainly for optical drives, while the latter are used for hard drives, floppy drives, and card readers      (Toshiba Satellite T4900 Battery)      .
  • Buttons and LEDs are typically located on the front of the case; some cases include additional I/O ports, temperature and/or processor speed monitors in the same area.
  • Vents are often found on the front, back, and sometimes on the side of the case to allow cooling fans to be mounted via surrounding threaded screw holes     (Toshiba PA3399U-2BRS battery)      .

Internal access

Tower cases have either a single side panel which may be removed in order to access the internal components or a large cover that saddles the chassis. Traditionally, most computer cases requiredscrews to hold components and panels in place (i.e. motherboard, PSU, drives, and expansion cards)     (Toshiba Satellite A200 Battery)      .

Recently there is a trend toward "screwless" cases, in which components are held together with snap-in plastic rails, thumbscrews, and other methods that do not require tools; this facilitates quick assembly and modification of computer hardware.

Appearance

Through the 1990s, most computer cases had simple rectangular shapes, and were often painted beige      (Toshiba Satellite 1200 Battery)   .

Beige box designs are still found on a large number of budget computers assembled from generic components.

Case modding is the artistic styling of computer cases, often to draw attention to the use of advanced or unusual components. Since the early 2000s, some cases have included clear side panels or acrylic windows so that users can look inside while it is operating (Toshiba Satellite M300 Battery)     .

Modded cases may also include internal lighting, custom paint, or liquid cooling systems. Some hobbyists build custom cases from raw materials like aluminum, steel, acrylic, or wood    WD passport essential (500GB/640GB) .

Case manufacturers

Prominent after-market case manufacturers include Ahanix, AeroCool, Antec, AOpen, Asus, Chenbro, Chieftec, Cooler Master, Ever Case, Foxconn, Gigabyte Technology, HEC Compucase, In Win Development, IXIUM, Lian Li, Lin Chi, CIRCLE, FRONTECH, ODYSSEY, ZEBRONICS, NZXT, OrigenAE, Raidmax, Shuttle Inc., SilverStone Technology, Thermaltake, Xclio, Yue Lin, and Zalman       WD passport essential (250GB/320GB) .

Intrusion detection

Some computer cases include a biased switch (push-button) which connects to the motherboard. When the case is opened, the switch position changes and the system records this change. The system's firmware or BIOS may be configured to report this event the next time it is powered on      WD  passport essential SE (750GB/1TB)      .

This physical intrusion detection system may help computer owners detect tampering with their computer. However, most such systems are quite simple in construction; a knowledgeable intruder can open the case or modify its contents without triggering the switch    WD  passport elite(250GB/320GB) .

Computer case screws

Computer case screws are the hardware used to fasten together parts of a computer case and to fasten the system components (such as motherboards,hard drives, and power supplies) to the case. Although there are numerous manufacturers of computer cases throughout the world, the computer industry has generally standardized on some specific screw thread measurements WD passport elite(500GB/640GB) .

The Unified Thread Standard (UTS) originates from the United States while the ISO metric screw thread is standardized worldwide. In turn, these thread standards define preferred size combinations that are based on generic units—some on the inch and others on the millimeter      WD  passport studio for Mac(320GB/500GB) .

6-32 screw holes are often found on expansion cards (such as PCI cards) and hard disk drives. M3 screw holes are often found on optical disc drives and floppy drives. 4-40 jackscrews are often found on connectors at the ends of certain types of cables  WD  passport studio for Mac(500GB/640GB) .

6-32 screw

The 6-32 is a UTS screw with a major thread diameter of 0.1380 inches and a pitch (distance between adjacent threads) of 1/32 in. It is by far the most common screw found inside computer cases and commonly appears in lengths of 0.15 and 0.25 in. Nearly every brand new computer case comes with a bag of these     WD  Elements series(250GB/320GB) .

They are used:

  • To fasten a power supply to the case
  • To fasten a hard disk drive to the case
  • To hold an expansion card in place by its metal slot cover
  • To fasten case components to one another      WD  Elements SE(500GB/640GB)
  • Usually, a 6-32 screw holds the main cover on the case. When it's not a 6-32, a larger 8-32 is the most likely alternative.

Of all the screws provided by computer case manufacturers, the 6-32 screw typically has the coarsest threading. They are almost always provided with aPhillips drive, accepting a #2 size tip (the larger of the two most common Phillips screwdriver tips) WD Elements SE(750GB/1TB) .

While a #1 size tip will drive the screw, it will be awkward to use and increases the risk of cam-out and damage to the screw head. They are less frequently provided with a hex head, even less with a pan head - a low disk with a chamfered outer edge. Because they are used in places where easy removal and replacement may be desirable WD  Elements desktop(500GB/640GB)

(such as on the side panels of the PC case), they are frequently available as thumbscrews with oversized friction-gripped heads that can be removed with one's fingers rather than with tools      WD  Elements desktop(750GB/1TB) .

6-32 screws will fit into holes threaded for M3 screws (the second most common type of screw in PCs), but this will damage the finer M3 threading. Also, when 6-32 screws are screwed into brass M3-threaded motherboard standoffs, the threads tend to become "locked", and the entire motherboard must be removed to separate them      WD  Elements desktop(1.5 TB/2TB) .

M3 screw

This screw is the second most common screw found in PCs . This is a metric screw, and just about every case manufacturer provides a package of M3screws as well as 6-32's. Specifically, the screw type is M3-0.50, meaning the threads of the screws are 0.50 millimetres apart. These screws, like the 6-32 screws, also typically accept a #2 size Phillips screwdriver tip  WD  passport essential SE (750GB/1TB)--USB 3.0)        .

M3 screws are used for fastening optical disc drives and floppy drives. They will fit in 6-32-threaded holes, but their narrower diameter and finer thread pitch causes them to seat only loosely in the hole. Nevertheless they are often placed there by amateur PC builders who are unaware of the distinction    WD  passport essential (500GB/640GB) .

M3 screws are also the most common screw used to secure a motherboard to motherboard standoffs.

Of all the screws provided with PCs, M3s are usually identified by them having the finest thread pitch of all the screws provided.

6-32 screws will strip the threads of M3-threaded holes     WD  passport for Mac(320GB/500GB) .

When the M3 hole is drilled into sheet metal (as on floppy and optical disc drives), a 6-32 screw that damages the threading will typically stay in the hole and can be removed fairly easily. When the M3 threading is into solid metal (such as a motherboard standoff), a 6-32 screw will get stuck before it can be screwed in all the way     WD  passport for Mac(640GB/1TB) .

Motherboard standoff

Most cases use threaded brass male-female standoffs for attaching the motherboard to the case chassis. Sometimes threaded or snap-lock plastic standoffs are used, which are less secure mechanically. Metal standoffs provide an electrical ground connection between the motherboard and case, while plastic standoffs do not      My book essential 4 generation  (640GB/1TB) .

The standoff provides a margin of space between the motherboard and the case. Without the space, the motherboard would be in physical contact with the case, which would cause it to not function because its various solder points would be in contact with the case's metal, which forms a short circuit with the computer's electrical ground    WD  My book essential 4 generation( 1.5TB/2TB) .

There is no rigid standard for what measurements a case's standoffs use. However, use of M3 and 6-32 threads is nearly universal. There is also no single standard for the height of the standoff; one quarter inch is common but not universal.

Each standoff has a "male" portion that screws into the case, and a "female" portion that receives a screw that has passed through a specially grounded pre-drilled hole in the motherboard       WD  My book elite( 1TB/1.5TB) .

Standoffs that use strictly M3, strictly 6-32, or a combination (male portion 6-32, female portion M3) are all fairly common.

It is good practice to tighten the standoff to the chassis with a nut driver or pliers, or use a thread locking compound between the male portion of the standoff and the chassis sheet metal       WD  My book studio(1TB/2TB) .

This ensures that if when detaching the motherboard, the screw that holds the motherboard onto the standoff will unfasten instead of the standoff becoming unfastened from the chassis. If tightening the standoff with a nut driver or pliers, be careful not to over-tighten, as the soft metal threads of the standoff and chassis are easily stripped or broken      WD  My book essential 4 generation( 1.5TB/2TB) .

Using a thread locking compound between the motherboard fastening screw and the female portion of the motherboard standoff is neither needed nor desired. Thread locking compound will not adversely affect the electrical ground path between the motherboard and chassis    WD  My book elite(640GB/2TB) .

It is a frequent mistake when building PCs to accidentally use 6-32 threaded screws into motherboard standoffs expecting an M3 screw. The result is that the screw will not go all the way, and the threads become stripped and "lock". Once locked, attempts to remove the top screw typically result in the entire standoff unscrewing from the case and potentially flexing the motherboardSeagate  expansion portable (320GB/500GB) .

In that situation, the screw and the standoff cannot be separated without removing the entire motherboard and subjecting it to potential damage while it is flexed in place.

4-40 jackscrews

Pairs of 4-40 UTS jackscrews are used to fasten certain connectors to hardware ports. The screws are typically located on either side of D-subminiature connectors such as on VGA, serial, parallel, and legacy game controller ports. They are also more recently used on DVI connectors      Seagate  expansion (1.5TB/2TB) .

The female 4-40 is usually just a removable standoff that has been screwed into the port with a relatively tighttorque. This standoff also often serves as a mechanical mounting either attaching a connector on a flylead to the case or attaching the backplate to an expansion card (connectors on the ATX IO plate are not normally attached to the plate)   Seagate  expansion (1.5TB/2TB) .

The screw has 40 threads per inch, and despite its threads visually appearing similar to M3, they are not interchangeable. In SI units, the 4-40 has a pitch of0.635 mm while the M3 has a finer pitch of 0.5 mm.

A typical length for a 4-40 screw used in PCs is 0.18 inches   Seagate  Freeagent Go(250GB/320GB) .

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