case : Computer Hardware Buyers’ Glossary

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case
The bigger the case the easier it is to service and the more room for expansion — with bays for adding extra an extra disk, tape drive, CD-ROM (Compact Disc — Read Only Memory), floppy, DVD (Digital Video Disc) etc. Small cases kink cables and overheat from lack of air circulation. Get one a little too big with easily removable side panels. Count up the hidden and exposed 5.25 and 3.5 inch bays you will need. Consider floppy, CDR, CDRW, DIVR, DIVRV, hard disks, mag tape backup, sound Control Panel, mag stripe reader…

Look for a recessed RESET switch so you won’t hit it by accident with your knee.

Most computers nowadays come in mini tower cases that can fit on the floor or desktop. Cases usually come in boring shades of beige. For $75.00 CAD (or less for multiples) you can have your computer, monitor and keyboard painted with a special plastic coating in any colour you want. The new Pentium IV motherboards require a slightly deeper case than usual. If you buy a new case, you probably should get that extra room just in case. Make sure your case and motherboard are compatible. Most cases and motherboards are ATX (Advanced Technology Extended) form factor. Motherboards are shrinking all the time, and cases are shrinking with them. There are also mini-ATX and micro-ATX cases.

The ATX spec, does not specify what I/O connections must be available on the back panel, but here is what they typically look like:

ATX case back connector

ATX case back connector

A more modern motherboard might present connectors like this:

Other possible connectors include HDMI (High-Definition Multimedia Interface) video, VGA (Video Graphics Adapter) video, USB-3, external SATA (Serial ATA), serial, parallel.

Modern motherboards consume more power and consequently give off more heat than computers of former years. Intel in response designed the BTX form factor, but it has not yet caught on.

Power supplies often come bundled with the case. Spend a little extra to get good quality and a slightly higher rating than necessary. A flaky power supply will cause no end of odd glitches.

Cases are usually sold without any fans. You will need to get at least one.

Cases, disks, motherboards etc. usually come without a full complement of screws and connectors. Before the sale, make sure these are all included.

Installing the Case

Modern computers are pretty idiot proof. Connectors are keyed and colour coded. However, cases are another matter. They have over a dozen separate connections that each must be painstakingly hooked up. This is quite ridiculous. it is a major factor in the cost of assembling a computer. There should be one plug that connects everything.

Usually all the little wires you need to connect all the USB (Universal Serial Bus) ports on the back panel to various spots on the motherboard are not included. Either you need to buy some separately, or mark the connections as not functioning. Otherwise later you will be very puzzled when you plug you mouse into one of the unconnected ports and it does not work.

You need tiny fingers for this job. Borrow a child.

The connections are almost never documented. You have to take the case apart to see where wires go, use a continuity meter and just plain experiment. Happily getting it wrong will rarely cause permanent damage, just frustration. With LED (Light-Emitting Diode) s, if the light does not work try attaching it the other way around. Happily, switches are not polarity sensitive.

Ask your case dealer to fill in a sheet like this on all the case connections. This sample chart is for a case 17" tower case I bought from DTI computers.

Case Connections
disk activity LED red + and white -
power on LED green + and white -
reset switch blue + and white -
ATX power switch orange + and white -. This is a low voltage switch to control the main AC (Alternating Current) power switch.
USB port red +5V power (Vcc), green + data, white — data, black ground
speaker red +, black -

Installing the Motherboard

Use the round screws with the saucer like tops. Use at least nine of them to mount your motherboard, offsetting with brown washers, top and bottom, each side of the motherboard. I am not sure the function of the washers — electrical insulation or mechanical padding. Eyeballing motherboards, they look as though they are designed not to need electrical insulation. The hexagonal brass risers screw into the case and support the motherboard underneath. There are spring like contraptions you can use where there are no proper holes in the case to fit the motherboard holes. Giving the motherboard solid support protects it from damage when you insert or remove components. Flimsy mountings mean it will bend and crack the traces when pressed. On the other hand, don’t overtighten the screws.

The back plate where the keyboard and other connectors poke through has mysterious little projections. These are to hold the plate in place by spring pressure against the back of the motherboard. They are not intended to be bent and wrapped around anything.

Installing the Hard Disk

Use the rounded mushroom-like small screws for mounting hard disks. Mount hard disks with as many screws as there are matching holes to fit. The more solidly the disk is mounted, the quieter it will be, the less it will vibrate and the longer it will live. Use the proper screws. Ask your dealer to give you some and have him test them before you leave the shop to make sure they are the right ones. If you use ones too long, you can puncture the airtight chamber on the disk. If you try to make do with the wrong screws you will strip the threads, then you will never be able to mount the disk properly.

Disks need good air circulation. Try to arrange empty bays top and bottom and a good air flow unimpeded by cables. You might even consider a fan dedicated to cooling your disk drives.

Motherboard Sizes

You must make sure your motherboard upgrade fits your case. Originally cases were all large enough to handle any size motherboard. Now the match is much tighter.

Motherboard Sizes
Form Factor Metric Size Imperial Size Aliases
width × depth width × depth
Mini-ITX17 × 17 cm6.69 × 6.69 in  
Mini-DTX20.30 × 17 cm7.99 × 6.69 in  
Taille Micro-ATX24.40 × 17 cm9.61 × 6.69 in  
Flex-ATX22.90 × 19.10 cm9.02 × 7.52 in  
DTX20.30 × 24.40 cm7.99 × 9.61 in  
Pico-BTX26.70 × 20.30 cm10.51 × 7.99 in  
Micro-ATX24.40 × 24.40 cm9.61 × 9.61 in Embedded ATX, µATX, M-ATX
Micro-BTX26.40 × 26.70 cm10.39 × 10.51 in µBTX, M-BTX
Baby-AT33 × 21.60 cm12.99 × 8½ in  
ATX30½ × 24.40 cm12.01 × 9.61 in Standard ATX
BTX32½ × 26.60 cm12.80 × 10.47 in  
XL_ATX34.30 × 26.20 cm13½ × 10.31 in Ultra-ATX
E-ATX30½ × 33 cm12.01 × 12.99 in Extended ATX
AT35 × 30½ cm13.78 × 12.01 in Standard AT
WTX35.60 × 42½ cm1.17 × 1.39 ft Workstation ATX, WATX

I refer to the depth as the distance from the front of the motherboard to the back where the slots and connectors are. I refer to the width as the distance between the two sides of the motherboard. Others may refer to these as the length and width or width and length. To figure out which terminology a given vendor is using, the bigger number is the width and the smaller the depth.

Make two Dymo sticky labels:

Access

and

Access on other side

Put the first on the cover for the side of the motherboard’s components. Put the second one on the cover for the side of the motherboard’s underside. This will help you figure out which panel goes on which side and which way is up. Later it will tell you which side to open to add some RAM (Random Access Memory).


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