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Case
Parts of the Case
/ Frame and Cover / Power
Supply / LEDs, Speaker and
Connecting Wires / Cooling Vents and Auxiliary
Fans / Mounting Hardware / Faceplates
and Expansion Slot Inserts / Styles
and Sizes / Case Location
/ Full Tower / Mid
Tower / Midi Tower / Mini
Tower / Desktop / Slimline
Case / Proprietary Case Designs
/ Comparison of Case Styles
/ Form Factors / PC/XT
/ AT / Baby AT / LPX
/ ATX / NLX / microATX
/ Drive Bays / External
Drive Bays / Internal Drive Bays
/ Drive Rails / Drive
Bay Sizes
More Glossaries: | Power Supply |
| How to Choose a Case? | FAQ - Cases | How to Choose a PSU? |
Case - The system case is the metal and plastic
box that houses the main components of the computer. While the case isn't
as critical to the system as some other computer components (like the processor
or motherboard, I mean, it's a box!. However it's definitely not just a
box.), it has several important roles to play in the functioning of a properly-designed
and well-built computer. Structure: The motherboard mounts into
the case, and all the other internal components mount into either the motherboard
or the case itself. The case must provide a solid structural framework
for these components to ensure that everything fits together and works
well. Protection: The case protects the inside of your system from
the outside world, and vice-versa. Vice versa? Yes, although most people
don't think about that. With a good case, the inside of your computer is
protected from physical damage, foreign objects and electrical interference.
Everything outside of your computer is protected from noise created by
the components inside the box, and electrical interference as well. In
particular, your system's power supply, due to how it works, generates
a good deal of radio-frequency (RF) interference, which without a case
could wreak havoc on other electronic devices nearby. Cooling: Components
that run cool last longer and give much less trouble to their owner. Cooling
problems don't announce themselves; you won't get a "System Cooling Error"
on your screen, you'll get random-seeming lockups and glitches with various
parts of your system. You'll also have peripherals and drives failing months
or years before they do on your friend's computer, and you'll never even
dream that poor cooling is the cause. Making sure that your system is cooled
properly is one good way to save yourself time, trouble and money. A spacious,
well laid-out case is a critical part of proper system cooling. Small cases
require components to be packed close together, which worsens cooling in
two ways. First, air flow through the case is reduced because it is blocked
by the components. Second, the parts are closer together so there is less
space for heat to radiate away from the devices that are generating it.
Organization and Expandability: The case is key to a physical system
organization that makes sense. If you want to add a hard disk, CD-ROM,
tape backup or other internal device to your PC, the case is where it goes.
If your case is poorly designed or too small, your upgrade or expansion
options will be limited. Aesthetics: The system case is what people
see when they look at your computer. For some people this isn't important
at all; for others it's essential that their machine look good, or at least
fit somewhat into their decor. In an office environment, PCs that all look
different can give a work center a "hodge-podge" appearance that some consider
unprofessional, for example. Status Display: The case contains lights
that give the user information about what is going on inside the box (not
a lot, but some). Some of these are built into the case and others are
part of the devices that are mounted into the case. In terms of its actual
operation, the case doesn't of course do a lot. It does have switches and
the above-mentioned status lights.
Top
Parts of the Case - A system
case should normally come with a number of physical components. This will
of course vary widely from system to system, depending to some extent on
the form factor and overall design of the case. If you buy a case by itself
for use in building your own machine, you should be able to check for all
of these items. If you bought a pre-built system, many of these components
were probably already put into the case when it was assembled, with left
over materials kept by the company that made it.
Frame and Cover - The physical
frame of the case, and its cover, are usually made of sheet metal. The
cover slides off the frame when the screws that hold it to the frame are
removed (though some cases use no screws at all to secure the cover, and
increasing numbers of designs use removable panels instead of an integrated
cover.) If the case is the most overlooked part of the PC, the quality
of the frame and cover is the most overlooked of the overlooked. Consider
the following when assessing the quality of the frame and cover of the
case: Rigidity: Many of the components in your PC have little tolerance
for being flexed or bent; this is especially true of the motherboard. A
very high quality case is made of solid, heavy gauge steel (16 to 18 gauge)
while slightly cheaper ones use lighter (20) gauge steel. All-steel cases
have very good rigidity, feel "solid", and will keep your system from flexing.
The next step down from all-steel is aluminum reinforced with steel. The
cheapest cases use punched aluminum that you can literally bend with your
hands. Fit: Quality cases have a good fit between their components.
The cover fits securely on the frame, and any plastic panels fit without
rattling or leaving large gaps. Proper fit also reduces spurious RF emissions
from the PC, and helps enable the case to be FCC certified. Finish:
Good cases have their metal properly finished and trimmed, while cheaper
cases often leave very sharp edges that can be hazardous to those who work
within them.
There are so many different configurations of cases and their covers
that it would be impossible to list them all. Many companies seem to pride
themselves in their ability to come up with wacky new case designs with
screws in the strangest of places, it seems. The following general categories
seem to cover a good chunk of what is out there, however: conventional
desktop, conventional tower, front-screw desktop, front-screw tower, single
screw tower/desktop, screwless tower/desktop and "Flip-Top" desktop.Another
relatively new innovation in case design is the removable, rotatable, or
slideable motherboard panel (sometimes called a "motherboard tray".) Many
newer, higher-quality cases are designed to allow the part of the frame
where the motherboard is mounted to be removed from the case or shifted
for easier access. If you've ever built your own PC, or tried to replace
a motherboard in an existing system, you know that this is a design that
is long overdue. It makes it much easier to work within the system, and
can make even a small case seem much larger.
The back of the main case frame will usually contain a number of cut-outs,
which are the places where I/O connectors from the motherboard are mounted.
On older XT, AT and Baby AT cases, these usually are smaller, individual
holes where your serial, parallel and other interface ports are mounted,
with wires that run to headers on the motherboard. Newer form factors such
as NLX and ATX have the I/O ports mounted directly onto the motherboard
in either a single or double row; cases designed for these form factors
are sometimes equipped with exchangeable plates that match different port
layouts, providing flexibility for changing motherboard designs.
Finally, don't forget your feet! They attach to the bottom of the case
to provide traction, especially on slippery desks. Sometimes new cases
come with their plastic feet not yet attached. Remember to install them
as soon as possible when assembling the case, as it may not be possible
to put them in once the motherboard and other components have been installed.
Larger cases occasionally come with wheels.
Power Supply - The power supply
usually comes with the case, even though it isn't technically part of it.
The power supply comes with an integrated fan, secured to the back of the
case in AT form factor supplies, or the front (to blow into the case) for
most ATX supplies. The power supply is discussed in its own section here.
The power switch for AT form factor cases is really part of the power
supply; for ATX form factor cases it is a separate component attached to
the case. The switch on most modern PCs is mounted just behind a plastic
button that is accessible from the exterior of the case. Most cases also
come with a standard power cord, usually black, to plug the power supply
into the wall.
LEDs, Speaker and Connecting
Wires - Most cases have at least two LEDs, to indicate power and hard
disk activity. Some have several more LEDs to indicate turbo status or
other functions (though "turbo" is now outdated and not generally seen
on new PCs.) A standard PC speaker is usually mounted somewhere inside
the case, but may be loose in a new case. There are special wires for all
the LEDs and for the speaker, to be connected to the motherboard or drives.
Cooling Vents and Auxiliary Fans
- Cooling vents are usually in the front of the case. These allow air to
be circulated by the power supply fan. They should not be blocked off or
poor cooling may result. Some cases come with extra, auxiliary cooling
fans, and/or mounting locations for the user to add fans if he or she desires
to do so. These are becoming more popular, especially with homebuilders
and overclockers, since they theoretically reduce the heat level within
the case. The most common location of additional cooling fans is the front
of the case, opposite the main power supply fan.
Mounting Hardware - If you are buying
a new case, it should come with mounting hardware. This normally comes
with the case, not the motherboard. Make sure you have mounting hardware
or your system assembly will stall in pretty short order. The exact hardware
included varies greatly and depends on what the manufacturer decided to
include in the case, but you will generally find some combination of the
following (since most cases will use a combination of mounting holes):
Plastic Standoffs: Also called "spacers", "sliders", and of course
the highly technical "thingamajiggies", these are generally made of white
plastic and are used for mounting the motherboard to system cases that
have large eyelet holes. They have a collapsible point on one end and a
round disk on the other. They were originally created to make motherboard
installation "easier" since they do not require screws, but in my opinion
they are just a pain to deal with because they make lining up the motherboard
more difficult during installation. Metal Standoffs: Again also
called "spacers" and a few other names (some of them unprintable), these
are 3/16" hexagonal nuts with a threaded screw on the end. They are usually
made of brass, sometimes steel, and they are used for mounting to threaded
holes in the system case. Screws: These are used to screw the motherboard
to the brass standoffs mentioned above. Washers: Generally made
of plastic or paper, these go under the screws to keep the screw head away
from the circuitry on the top surface of the motherboard. These are now
sometimes being omitted in new system cases because they are less necessary
now than they once were (since motherboards today now tend to keep the
circuitry farther away from the screwholes than they once did). Some cases
actually come with their mounting hardware fixed into position and not
movable. In theory, a time-saver, but it reduces your flexibility in the
event that you want to upgrade down the road.
Faceplates and Expansion Slot Inserts
- Plastic faceplates (sometimes called bezels) are provided for drive bays
that are not in use. Some cases come with these pre-installed while others
do not. Make sure all open bays are covered, to improve air flow and cooling,
and keep foreign materials out of the computer. A good case should also
come with metal expansion slot inserts to cover the space used by slots
that don't have cards in them. Watch out for the newer (usually cheaper)
cases that just use stamped metal to cover these slots. Once you punch
one out you can't put it back in. If you change a card's slot, you will
need the kind of inserts that screw in place to cover the hole you left.
Some of the cases with stamped metal slot covers also come with real ones
you can screw in place later if you need them, but some don't! Leaving
expansion slots open adversely affects air flow in the case, and thus cooling,
and also increases the chances of system contamination.
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Styles and Sizes - Cases
come in several different major styles. Despite the commonly-used names,
such as "tower", "mini-tower", etc., there are no standards for case size
or shape, and one company's full tower case can be very different in details
from another. Some of the companies that make high-quality high-end cases
incorporate very interesting features into their cases that stretch their
capabilities for the same amount of space taken. As a result, one company's
"mini-tower" may be able to hold more components, and cool them better,
than another company's "mid-tower". The two basic styles for the case are
the tower case and the desktop case. You've no doubt seen each of these
before; the desktop is a rectangular case that is wider than it is tall
and normally sits on the desk. The tower is like a desktop flipped on its
side and can sit on the floor or on the desk.
Case Location - In deciding
what style case you want your system to have, the first consideration should
be the case location - where you want to put it. There are generally two
choices: on the desk or on the floor. Putting the case on the floor gets
it off your desk, saving desk space. However, it also means that the power
and reset buttons, the indicator LEDs, and the drives, are less accessible
to your fingers, and more accessible to accidents involving your feet.
This is in some ways, the biggest drawback of a tower case. In some cases
you will need cable extenders for your keyboard, mouse or monitor, depending
on your setup. Also, if you are getting a smaller-sized monitor, say 15",
you may need something to put under it so that it is at a comfortable reading
level (larger monitors usually work better on the desktop directly). Finally,
there's the chance the box will get kicked or knocked over, or you'll hit
the power switch with your knee at the worst possible moment (Murphy's
Law--ignore it at your peril!). A tower case is generally recommended for
a floor location, for stability. You can put a desktop on the floor, on
its side, as long as you secure it properly (you don't want the box falling
over on you!) If you do go with a desktop on the floor, some companies
sell (used to sell?) brackets intended to support desktops put on their
side; you may still be able to find one of these. A desktop case is of
course better for putting the machine on the desk; a tower case can be
put on the desktop but it will take twice as much room since the monitor
can sit on top of a desktop case but not a tower. One final consideration
is the orientation of your drives, in particular CD-ROM drives, DVD drives,
and other removable media. Many of these drives will not tolerate being
mounted on their side, which means you need to consider how the system
will be oriented in advance. Most modern hard drives will operate just
fine mounted either vertically or horizontally.
Full Tower - A full tower case
is the largest standard PC case available on the market. These units are
big, heavy and at two to three feet in height, are intended to be installed
on the floor. Full towers are the most flexible, expandable cases, with
many drive bays to support a large number of internal devices. They normally
come with larger power supplies to support these devices (but not always)
and since they are so roomy, they are the easiest to work in and the best
at keeping components from overheating. They are, naturally, also the most
expensive type of case.
Mid Tower - A mid tower case is
similar to a full tower case, but slightly smaller. This size seems to
be all over the place; some companies make mid tower cases that are no
larger than others' mini towers. A mid tower is a good compromise for those
that want more space than a mini tower offers, without going to the expense
of a full tower case.
"Midi" Tower - At first, there
were only full-sized tower cases. Then came mini-towers, and mid-towers,
which were a compromise between full-sized towers and minis. Then the marketing
people got to work--Scott Adams had it right on them--and produced the
"midi" case. It's hard to get a consensus on exactly what a "midi" case
is. Some contend that the name is based on a cutesy combination of "mid"
and "mini", and that the midi tower is therefore one that is smaller than
a mid tower but larger than a mini. Others use the term "midi" interchangeably
with "mid"; this seems to be more common in Europe than in North America.
Mini Tower - Currently one of
the most popular styles for new PCs, and the most popular of the stand-up
style case, the mini tower is the case of choice for many homebuilders.
It is roughly the same size as a desktop case, but due to its design is
generally easier to use and often has more capacity. It also tends to keep
components cooler than a desktop case. Since it is not nearly as large
as a full tower case, many people put the mini tower on the desktop, next
to the monitor. This is particularly preferable if you are using a larger
(17" or larger) monitor. Putting an 80 pound 20" monitor on top of your
desktop case is not good for your eyes, and not good for the system either!
Desktop - The desktop has been the
de facto standard for PC cases since the original IBM PC, XT and AT machines,
which came in a desktop case only. Today's desktops are different from
those, both in size and construction, but the idea is the same:
the box sits on the desk, and the monitor sits on the box. For those who
don't want to (or cannot) put the case on the floor, the desktop actually
saves space compared to a tower case, since the monitor won't sit on top
of a tower case. A desktop doesn't, in general, let components cool as
well as a similarly-sized tower, and the monitor sitting upon it can be
part of the reason.
Slimline Case - Also sometimes
called "low profile" or even "pizza box", this is a smaller version of
the desktop case. It was invented in part as a cost-cutting measure but
at least as much in order to reduce the amount of space the box takes up
on the desk. For many people, this case is aesthetically pleasing because
it takes up the least space on the desktop. Unfortunately, it fares rather
poorly in every other regard. These cases have little capacity for additional
drives, have the poorest expandability, are hard to work in, and have the
worst cooling. Despite this, more and more slimline PCs are being sold
today. The reason is simple: smaller cases are cheaper to build than bigger
ones, and many people underestimate the performance and longevity drawbacks
of tiny cases.
Proprietary Case Designs
- In addition to the standard case styles, there are some machines that
use totally unique designs. Some Compaq models for example have the monitor
and case in one large box. These machines are generally marketed to the
home user or first-time buyer as a "home appliance" and the idea is supposed
to be that this is "simpler" than having the monitor be in a separate box.
The disadvantage of this design, aside from the fact that it is totally
proprietary and therefore hard to upgrade, is that if you want to upgrade
your PC you lose your monitor, and similarly, if you decide your monitor
is too small and want a larger one, you have a problem because your PC
is in the same box. I strongly recommend against integrated units because
of their inflexibility. For servers and other high-end machines, special
cases much larger than standard full towers are available. These large
cases often incorporate special features such as locking front covers,
slide-out drive bays and wheels (since they are heavy). They can cost as
much as an entire regular PC by themselves. In addition to server-oriented
full-sized cases, there are special enclosures for such things as RAID
(disk) arrays available from major case manufacturers.
Comparison of Case Styles
- The key features in comparison of case styles are case size, number
of external bays, number of internal bays, cooling efficiency, power supply
and cost. The number of bays depends on the case, but it's much more likely
to find more bays in a full tower than a mini tower. For external bays,
the first number is how many 3.5" bays the case typically will have, and
the second is how many 5.25" bays. Internal bays are usually 3.5". Power
supply ratings are measured in watts (W). Getting a full tower case is
no guarantee of a 300 watt power supply, but it's much more likely to find
one in a full tower than a mini tower.
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Form Factors - In addition to coming
in different styles, cases also come in different form factors. The form
factor describes the general layout of the case, the positioning of the
slots in the back of the case, and the way that the case matches to the
major components that fit into it. In particular, there are three main
components that must be matched in terms of their form factor: the case,
the power supply, and the motherboard. Usually, when you buy a system case
it comes with a power supply, so matching the case and power supply is
not a concern.
The most popular case form factors today are the "Baby AT" and ATX
styles, with the smaller microATX/SFX form factor also being used increasingly.
These cases are not interchangeable, since they are shaped differently,
and require motherboards with a different form factor. If you are building
your own system you must ensure your motherboard and case/power supply
form factors match. There are some cases that can handle both baby AT and
ATX motherboards.
Not all case styles are available in all form factors. Increasingly,
as "Baby AT" loses in popularity to ATX and its variants, many newer cases
are becoming hard to find in the Baby AT format. The older form factors
(PC/XT, and AT) are not used in modern systems at all.
PC/XT Form Factor - The original IBM
PC, and its hard-drive-equipped successor, the IBM PC/XT, used the same
original PC form factor. These boxes were sold as desktops only, and were
constructed of heavy-gauge metal throughout (they don't make 'em like that
any more, for the most part). Many older PC buffs remember what these cases
were like: a "U-shaped" metal cover was fastened at the back using five
screws. To open the PC you had to remove all the screws and slide the cover
off the front of the base of the machine, sometimes risking the loss of
a floppy drive faceplate in the process. (Maybe it's a good thing that
they don't make 'em like that any more!) The power supply was tucked into
the right rear of the box, and the system power was controlled by a red
toggle switch (that was usually hard to reach).
These original PC boxes were also very large, and their power supplies
large as well, for the amount of power produced. (How many folks realize
that the original IBM PC's power supply produced only 63.5W? This was doubled
to 130W for the XT.) The PC/XT form factor was replaced by the AT form
factor when the IBM PC/AT was released in 1984, though IBM PC/XT cases,
as well as large numbers of clones, continued to be found on the market
for some time.
AT Form Factor - The "new" IBM PC/AT didn't
look all that much different on the outside from the PC/XT units it replaced;
but on the inside it was a different story. The AT case was functionally
similar the older PC/XT style, but was changed slightly so that it represents
a different form factor. The power supply was larger than in the PC/XT
and the positioning and size of the motherboard and power supply different.
Therefore, the PC/XT and AT formats were not compatible.
The AT form factor was very popular in the late 1980s, and was the
basis of many "clone" manufacturers' units (for compatibility with IBM.)
The AT system was also the first to formally introduce different desktop
and tower configurations. The desktop configuration was very similar to
that of the PC/XT, with the familiar red toggle switch in the rear of the
machine, on the right-hand side. The tower configuration saw the introduction
of the now familiar "remote" power switch, controlled by a button on the
front of the case. Due to its convenience, this was very popular and became
the standard for most later designs, both tower and desktop.
Baby AT Form Factor - Not long after
the introduction of the IBM PC/AT and the AT form factor, a smaller version
of the AT form factor was created called the "Baby AT" form factor. Baby
AT is similar to AT, except that it is smaller in the width dimension.
This means that Baby AT power supplies and motherboards will fit into full-sized
AT cases, but not vice-versa.
As AT-style machines took the world by storm, manufacturers quickly
developed a preference for the Baby AT form factor over the AT form factor,
since it provided the same capabilities at reduced cost. Users also preferred
the smaller Baby AT cases to the full-sized AT ones. As a result, Baby
AT quickly overtook AT machines in popularity. Until the rise of ATX, Baby
AT form factor PCs dominated the industry. Baby AT cases are found in both
desktop and tower configurations, like AT, and in a large variety of styles,
shapes and sizes. Baby AT cases are used with Baby AT style motherboards,
which can be recognized based on their dimensions and placement of components.
In the last couple of years, the ATX form factor has started to rapidly
push Baby AT out of the market. Led by Intel, as more and more motherboards
are offered only in ATX, the demand for Baby AT cases diminishes. However,
due to the large upgrade market, and the enormous installed base of Baby
AT machines, you should still be able to find Baby AT cases for some time
to come.
LPX (and Mini LPX) Form Factor - Without
knowing it, retail PC customers have made LPX one of the most popular form
factors of the last decade. Most PCs sold in slimline or "low profile"
cases in the late 1980s and early 1990s use the LPX form factor, or a variant
of it. Originally developed by Western Digital Corporation back when they
made motherboards, the goal of the LPX design was simple: to reduce the
size and cost of the PC system box. The key design decision in LPX that
enables the dramatic reduction of the size of the case is the creation
of a riser card that plugs into the motherboard. Expansion cards then plug
into the riser card, parallel to the motherboard. By doing this, the case
no longer has to be tall enough to accommodate the height of an expansion
card. One problem with the LPX form factor is that it is only a "pseudo-standard";
it was never formalized into a hard standard, the way for example ATX and
NLX have been. Many companies make systems that use slimline cases and
LPX-style motherboards and power supplies, but they often differ slightly
in size, shape, or other characteristics. This means you cannot expect
to move a power supply from say, a Compaq LPX system into a similar-looking
Packard Bell system. LPX systems are essentially proprietary.
There is one innovation of the LPX form factor that has carried forward
into the more modern ATX and NLX designs: the use of integrated I/O connectors,
and holes provided for them in the system case. The lack of this design
in the Baby AT form factor led to increased cost and time of assembly,
a problem avoided with the newer form factors.
ATX (and Mini ATX) Form Factor - The
first significant change in case and motherboard design in many years,
the ATX form factor was invented by Intel in 1995. It is continuing to
gain in popularity and is now surpassing the Baby AT form factor for use
by small PC shops and homebuilders (it has been the form factor of choice
for brand-name systems for some time.) The ATX design has several significant
advantages over the older designs, but the enormous installed base of existing
Baby AT cases and motherboards has caused the change to ATX to take many
years.
The ATX case is similar to a Baby AT case except that the holes in
the back are altered to fit the changed design of the ATX form factor motherboard,
in particular the integrated I/O ports. The ATX case also uses a different,
ATX power supply. Most ATX cases have more features than AT cases because
they are newer, and they are sometimes more expensive for the same reason.
The advantages of the ATX design are discussed in the form factor chapter
on motherboards.
Millions of older Baby AT systems are in existence, and to make it
easier for their owners to upgrade gradually to the ATX form factor, many
high-quality ATX cases will also accommodate Baby AT motherboards. (Having
a case that can handle either form factor motherboard also makes production
easier for the manufacturer.) Sometimes additional hardware or slight modifications
are needed to the case to switch from Baby AT to ATX or vice-versa.
Intel has also specified a "Mini ATX" motherboard size, which is slightly
smaller than the full-sized ATX specification. These boards use the same
ATX form factor power supplies and cases. microATX however is a different
form factor entirely.
NLX Form Factor - NLX is Intel's proposal
for the future of mass-marketed, retail PCs, replacing LPX. It is similar
in overall design to LPX, with a riser card arrangement and low profile,
slimline case. However, it has been updated and modernized to allow support
for the latest technologies while keeping costs down.Many slimline systems
that were formerly designed to fit the LPX form factor are now moving over
to NLX. One extra advantage of NLX over LPX is that it is a true standard,
unlike LPX, making interchangeability of components more likely than it
was for the older form factor. NLX seems destined to become of the most
popular form factors in the PC world, complementing the ATX "family" of
form factors.
microATX/SFX/uATX Form Factor - Computer
manufacturers continue to want to shrink the size of their systems, and
Intel has been happy to oblige, with another variant on the basic ATX theme
called "microATX". As the name implies, microATX is not only smaller still
than Mini ATX, it is actually smaller than even NLX. microATX is intended
for the very low end market that Intel has decided to target with force.
Technically, it could be said that microATX is not even really a case
form factor, because microATX is in fact a motherboard standard. However,
with the smaller microATX motherboards, manufacturers are creating smaller
cases to fit. To complement microATX, Intel created a new, low-output power
supply design called SFX. SFX power supplies are designed to work with
not only microATX systems, but also NLX and regular ATX systems, and this
is why these power supplies were not called microATX. SFX and microATX
are sometimes used interchangeably, or together, in describing this general
physical format. The term uATX may also be used to refer to microATX form factor.
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Drive Bays - Drive bays are the
spaces in the system case where you mount your hard disk, floppy, CD-ROM,
tape and other drives. They come in two general types, external and internal,
and two sizes: 5.25" and 3.5".
External Drive Bays -
This is a bit of a misnomer, since external means "outside" and these drive
bays are certainly inside the case. However, they are called "external"
because they allow access to the device from the outside. Any drive that
uses removable media or has controls that must be operated manually must
go in an external drive bay. This includes floppy disk, CD-ROM, DVD, tape
and removable-storage drives.
Internal Drive Bays - These
bays are entirely within the case and are not accessible from the outside.
If a device does not require any access from the outside it is preferable
to use an internal bay, and save the case's external bays for drives that
need them. In practical terms, this means that internal drive bays are
usually used for hard disk drives, which do not require any access by the
user. You can of course mount a hard drive into an external drive bay.
So in some ways, an internal drive bay is really an "internal only" bay.
Some cases in fact do not have any internal drive bays; hard drives are
mounted into external drive bays and solid faceplates left to hide the
drive from the outside.
Drive Rails and Brackets - Up
until a few years ago, most PC cases used drive rails--thin strips of metal
that interfaced drives to the case. Each drive that you wanted to mount
into the case was actually screwed into a set of two rails. The drive-on-rails
then slid into rail slots in the drive bays of the case, and the end of
the rail either snapped into place or was screwed into the front of the
case frame.
Newer cases, introduced over the last few years, have mostly done away
with drive rails. Instead of mounting the drive on rails, the drive is
mounted directly into the drive bays. This simpler design became more popular
than designs using drive rails for many years. Some companies have now
brought back drive rails with some of their models.
Some folks do like drive rails though. The only advantage to them that
I can think of, is of relevance only if you are someone who tinkers with
your PC a lot, swapping drives in and out or moving them between cases.
The rails make it much faster to move drives from machine to machine. In
mass-manufacturing environments, the design can also save time due to division
of labor, since one person can exclusively mount drives into rails or brackets,
which can be integrated into the main case frame quickly. This of course
doesn't apply to an individual PC builder.
Some cases use a snap-in bracket for internal hard disks. These are
a nice feature, because they let you remove the bracket, mount the hard
disk, and then remount the bracket with the hard disk. Alignment is slightly
more difficult than direct-mounting of the hard drive, but since exact
alignment is not critical for an internal drive, this is not a major concern,
and the bracket is easier to work with than bending your arms to access
the inner recesses of smaller cases. The only difficulty with this design
is that once the entire system is installed, cables or other devices may
make it difficult to remove the bracket for servicing.
Drive Bay Sizes: 3.5" and 5.25"
- Not surprisingly, these sizes correspond to the two common sizes of floppy
disks in use today. (Actually, the 5.25" disks aren't really that common
any more, but they're still out there.) The bays are not actually this
size, because this is the size of the media and the drive obviously must
be larger, but they are almost always referred to by those names. A 3.5"
bay is actually about 4 inches wide, and a 5.25" bay about 6 inches. While
these bays were designed to fit the two sizes of floppy drive mentioned,
all modern drives have all been designed to fit into the same dimensions.
Some devices require the larger size bay. Obviously, a 5.25" floppy
drive needs one, and so do all CD-ROM and DVD drives (CDs and DVDs are
4.75 inches wide). Many tape drives do as well, as do many removable storage
drives. A 3.5" floppy drive will of course fit in a 3.5" bay. So will most
modern hard disk drives (in fact, most internal drive bays are 3.5" for
that reason). The height of the different bay types is pretty much standard;
a 3.5" bay is about 1" in height, and a 5.25" bay is about 1.75" in height.
It is possible to buy adapters that will make a 3.5" device fit into a
5.25" bay, if you need to do this. It is easier to do with a hard disk
than a floppy disk or other device with a faceplate, because in addition
to the mounting rails for the side of the drive, you need an adapter for
the faceplate as well in the latter case.
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great insides - Oct 15, 2003
Reviewer: Keasar
real problems are solved with simple solutions, overlooking minor details like it's explained here could cost time and money. thaks.
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