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Computer-Case
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If you are purchasing a ready made computer (e.g. HP, Sony, Apple, etc.) you don’t need to worry as much about this discussion.  You simply want to make sure that you purchase a computer which will not only (1) fit into the available space on your desk or shelf, while allowing for full ventilation, but also (2) have the number of components, bays and ports that fulfill your computing needs.  Even so, the information below may make you a more informed computer shopper.

On the other hand, if you are building a computer or having one built, it is important to understand how the size of the computer case (sometimes called a tower, or a box, or a CPU) determines the size and type of the motherboard, drive bays and ports which comprise the computer itself.

After all, a computer case is essentially an enclosure.  It’s designed to neatly store all of the necessary components for your system, with a design optimizing the flow of air and fans to maximize cooling.   Theoretically, you don’t need a case; you could lay out all of the components on your desk and run the wires and cables between them.  But that would be ungainly.  At the other extreme, you could add all the glass viewing panels and neon lights to make it appear prettier, and (aside from overheating heating the enclosure) it won’t add to the intent or performance of the case.

So let’s start.

-> Computers can come in various colors and designs.  Some have more or less flashing lights.  Some cases have designs and pretty colors.  Some have different types of access panels, or are made of different materials.  But none of these things are particularly important.

-> Most important is the size (“footprint”) of the case itself.  Traditionally, computers come in three or four standard sizes:  Full, Mid and Mini Tower (desktop) cases, as well as various so-called smaller form factor (SFFs, like the Dell Optiplex line) and specialty (e.g. the Apple Mini (photo above right), G5 or some of the HPs and Sonys, where everything is built into the monitor, and the monitor is the case!).  The dimensions shown below are pretty much consistent:

 

Average Case Dimensions

 

Height

Width

Depth

Full Tower Cases

24"

8"

18"

Mid Tower Cases

18"

7.5"

19"

Mini Tower Cases

14"

7"

15"

Small Form Factor Cases

9"

10"

14"

Desktop/HTPC Cases

6"

17"

16.5"

FULL

MID

MINI

SFF

DESKTOP

-> Aside from how much space the computer takes up, why is this so important?  Actually, because the size has a direct effect on the components within the case.  The full tower case can hold a larger power supply, a larger motherboard (which may mean a larger processor with a larger heat sync and fan), more internal card types (e.g. PCI and PCI express) and extra slots and more external bays and ports on the back of the case.  The smaller cases, of course, hold less.  Moreover, the board connectors on an ATX case (to the power supply, for example) will vary from a different board like the AT/LPX, dictating the other hardware that will be connected to it. (See, e.g. power supplies, below)

-> One of the primary restrictions, one that drives most of the other considerations, is the size of the motherboard.  For motherboard form factors, see motherboard.  The chart below shows the limitations on the type of motherboard that can be used inside the various cases:

Motherboard Fitting Chart

 

Extended ATX

ATX

Micro-ATX

Full Tower Cases

Yes

Yes

Yes

Mid Tower Cases

Maybe

Yes

Yes

Mini Tower Cases

No

Maybe

Yes

Small Form Factor Cases

No

No

Yes

Desktop/HTPC Cases

No

Maybe

Yes

-> Now, let’s consider bays.  Bays are the slots that drives fit into.  They’re for hard drives, floppy drives, disk drives, CD/DVD drives, Zip drives, etc.  Some drives, like the hard disk drive, fit inside the case, and they’re internal.  Others are outside the case, and they’re called external.  As you can see below, there are limitations on the number of both internal and external drives imposed by the case and its motherboard:

Bay Fitting Chart

 

External 5.25”

External 3.5”

Internal 3.5”

Full Tower Cases

5+

2-3

3-6

Mid Tower Cases

4

2

4

Mini Tower Cases

2

1-2

4

Small Form Factor Cases

2

0

2

Desktop/HTPC Cases

2

2

3

-> The case and the motherboards will also cause limitations on the number and types of ports, or physical connections, that are available on the computer.  Some cases will have 3, 4 or 6 USB ports in varying (e.g. USB-2, USB-3) combinations, either all in the rear of the case, or perhaps two or more on the front.  Some will have all connections:  USB, maybe also FireWire, maybe even Thunderbolt.  But beware:  Some will not have PS2 ports for the keyboard and mouse (particularly Dell desktop computers, which stopped using them years ago), instead relying on USB ports for these devices.  Increasingly, many computers will no longer have parallel, Firewire, SCSI or serial ports.  Firewire ports are disappearing on PC (not yet Apple) laptops, while the faster Thunderbolt (a la USB-3) is showing up on Apple laptops.  There is a trend toward more and faster USB ports (the really fast “USB 3” ports are becoming more common on most newer boards) in place of these older type ports.  (Click HERE to see photos of these connectors.)  However, if you have older printers which use parallel cables, or special devices (label printers, backup drives, etc.) which use serial cables, keyboards and mice which require PS2 (maybe even DIN) ports or the like, you have to make sure you have that capability, which will be dictated by the case and the motherboard.  Also, check to make sure that the newer operating system required by the newer board will support backward compatible drivers for these ports.  (For example, a board which supports Windows 7 may not have drivers for your old Windows XP hardware, so you won’t be able to backwards install to the Win XP O/S using that board.) Of course, you may be lucky:  For desktops, there are many add-on PCI cards for USB-3, serial, parallel and other ports.  For laptops, the choice is more limited:  There are adaptors to convert between serial, Firewire, parallel and USB, and they may suffice.  But be sure to test them first, as they don’t always work as advertised with all devices, depending on hardware and drivers, and you could be taking a chance. [This discussion purposely leaves out pads and tablets, which strictly speaking aren’t cases, don’t have cards, and are self-contained.]

-> Finally, there is the matter of the materials that the case is made of.  One of the primary considerations in building a computer is the ability to vent heat from the motherboard, as the chips and other hardware become quite hot.  Most computers these days have at least two (processor and case) and quite often three fans perpetually running.  Aside from the consideration that the computer must be physically placed to maximize the venting of the air pulled from inside the machine, there’s also the matter of building the case out of a material that will keep it cool as well.  Steel is the most common material used to construct cases.  Not only is it strong, it is relatively inexpensive.  Aluminum is even more desirable, as it moves heat more efficiently, but is more expensive.  Acrylic materials may look nifty, but should generally be avoided, as plastic is not a very good heat conductor. And putting those neon lights inside just adds to the heat.

-> Now that you’ve got through the choice of your case, you’re ready to purchase the component electronics you’ll want to build your baby.  One thing to consider in this regard:  Some computer cases come with the power supply included.  Power supplies  (“PSUs”) are the devices that convert house current into lower voltage current that can then be applied to the motherboard, other boards and cards, drives, etc.  Power supplies vary in quality and power and have elements that are covered inthe above link. Most of the time, the power supplies that come with the case aren’t the best.  I personally believe that the power supply is an important part of your computer.  A poor one will blow out in the face of power fluctuations, or won’t last for a long time.  If it fails, it may take your motherboard, RAM chips and/or drive with it.  This can be an expensive repair, one that can be remedied by spending only slightly more on the power supply.  We generally put in at least a 500 Watt power supply, and usually only from a handful of reputable manufacturers.  That additional twenty or thirty dollars can make a huge difference. Your computer may only use 100 watts of power when it’s running, but it may require 250 watts when it boots, so you’ve got to get a power supply for that moment of electrical requirements.  Compare this calculation to the “cold crank amps” that rate your car battery, where its power must meet or exceed that required to crank the motor from a dead start, even though it requires very little power once the car is running.   For an excellent on-line calculator for the necessary wattage of a power supply for your computer, click HERE.

Bet you didn’t know that selecting your computer case was much more than just a cosmetic choice!

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