Chapter 15: The System Case^365
have two wires, one that is either black or white and one that is some other
color, which have to be precisely connected to the motherboard. Normally,
the colored wire is positive and the black or white is the ground. If they are
connected backward, the LEDs simply don’t work—no harm, no foul.The speaker also has two wires that connect to the motherboard with either a four-pin
connector or two single-pin connectors. Once again, if it is wrong, it just doesn’t work.Cooling Vents
Although it may seem obvious, air must have a means to get into or out of the system
case. Usually, the case has a grouping of small vent holes, cuts, louvers, or the like. A big-
ger case cools the internal components better than a smaller case because of its larger air-
flow, but both must still have a way to vent the case. You can assume that any case you
buy from a reputable manufacturer (such as those that have been kind enough to supply
figures for this chapter) have engineered their cases to properly cool them.
When assembling a system case and its components, be aware of where the vents are
and take care not to block them.Mounting Hardware
If you are buying a new case, it should come with mounting hardware. These pieces nor-
mally come with the case,notthe motherboard. Make sure you have the appropriate
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 in-
clude 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 These small plastic parts are also called “spacers,”
“risers,” and “sliders.” The standoffs used inside the system case to mount
the motherboard are typically small plastic legs (see Figure 15-22) that snap
into the mounting holes on the motherboard and then slide into the mounting
slots on the case. In addition to anchoring the motherboard in place, the standoffs
keep the motherboard from contacting the system case and grounding or
shorting itself.
Metal standoffs Metal standoffs are largely obsolete now for two reasons:
they are a bother to work with, and they cost more than the plastic type.
However, if you have a case that has threaded holes in place of mounting slots,
these brass hexagon spacers need to be used. The standoff has screw threads
on one end and a threaded screw hole on the other end. The screw end is
screwed into the case; the motherboard, along with some insulating Teflon,
Delran, or paper washers, is attached to the other end with a screw. The