| Expansion slot blanks with ventilation holes[1] |
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Desktop cases and power supplies often come as a package. Cases come in various sizes and styles to match motherboards and aesthetics.
The most popular desktop cases are tower-style. Regularly, a tower case is designed to stand on the short side. There are mini-tower, mid-tower, and full-tower sizes to suit the motherboard's needs and optional equipment.
A desktop case is designed to stand on its long side in regular use.
Regardless of style, cases are designed with internal airflow in mind to aid in cooling the components.
Myth:
Unused expansion slots must be closed with a blank placeholder to ensure proper air circulation in the case. Air should be pulled in through the various seems and exhausted by the power supply fan.
It was once thought that the best cooling occurred when air was blown out of the case rather than into it. Tests by NCR in the 1970s showed that their equipment was better cooled when they reversed the fans to blow air into the case. This information was very slow to percolate through the rest of the industry.
Modern computer cases have multiple fans blowing air into and out of the case at various positions to ensure good cooling and plenty of openings for air to enter and exit the case.
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Expansion slot blanks occasionally have ventilation holes to aid cooling.
Less expensive cases are usually assembled with screws that must be removed to open the case. More expensive cases often have latches that open quickly, allowing easy access to internal components.
Do not over-tighten the case assembly or device mounting screws; you are not torquing the heads on your Chevy. If you overtighten the screws, you will either strip the threads of the screw or tear a hole in the sheet metal or plastic of the case or device. If you are tightening more than you can by holding the screwdriver with your thumb and forefinger, you are over-torquing the screw.
Computer cases have mounting holes (or other mounting devices) in various places to match various motherboards. Each hole that matches a hole in the motherboard must have a standoff to mount the motherboard. Be careful not to put standoffs where they are unneeded because they may short the motherboard to the case.
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Some standoffs may be nylon, which match slots in the case. The motherboard is snapped onto these standoffs.
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The motherboard can be removed from nylon clip standoffs by compressing the clip with needle-nose pliers. A metal or plastic tube with an inside diameter that matches the closed clip easily compresses the clip for motherboard removal.
Most computer cases that use screws to mount the motherboard come with those screws and insulated washers (usually red paper impregnated with a reinforcing material).
Curiously, they don't supply enough of these washers to insulate the motherboard from the mounting screws and standoffs, as that would require two washers for each screw. Furthermore, the motherboard mounting holes are made such that connections to the motherboard ground trace surround them. This implies that the motherboard ground is expected to connect to the case ground (which should connect to a true Earth ground via the power supply and cord).
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The question is: should you use these insulating washers when assembling a computer? The answer is to act according to company policy. Keep in mind that the end user may inspect the end product and protest if the washers aren't in place. If you assemble a computer for someone else and don't include the washers, be prepared to confidently explain that the washers do not apply to that situation. If you search the Internet, the consensus is that the washers are unnecessary.
Every case has a power switch and several LED indicators.
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The motherboard has a header for these connectors.
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Each manufacturer arranges the pins on these headers by their design. However, they are usually clearly labeled. The above header has no speaker connection (which has two unused pins between the two used pins), as the motherboard has a built-in speaker.
Connecting to the header is simple. Only the LEDs are polarized, so the power switch, reset switch (if present), and speaker can be connected without regard to orientation. The LEDs are polarized, so there should be an indication of which pin is which. However, if they are connected backward, they simply won't work. Flip the connectors if the LEDs don't light at the appropriate times.
Computer cases come with mounting bays originally designed to fit half-height 5.25-inch floppy drives. As 5.25-inch floppy drives are long obsolete, various hard and optical drives have been designed to fit the same bays. Now, they come with mounting hardware to fit 3.5-inch hard drives. Adapters are also available to fit 2.5-inch notebook drives that fit 2.5-inch SSDs.
Most hard drive mounting bays are oriented toward the front of the case. This was necessary for floppy drives and is still necessary for optical drives. However, hard drives are sometimes mounted in odd places, like above the power supply or behind a fan at the front of the case.
Before the demise of floppy disks, cases came with bays for 2.5-inch floppy drives. Many of these cases are still in service, but new cases are not made with floppy drive bays.
Many cases have more drive bays than are needed. Other devices are made that fit drive bays to use the available space. For example, memory card readers and USB expansion ports are available in form factors that fit hard drive and floppy drive bays.
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