the card into the system bus structures. An expansion slot contains metallic, typically copper,
springy fingers that clamp onto the expansion card’s edge connectors when the card is
inserted into the slot. The edge of an expansion card has metal connectors attached that will
match u pto the fingers of the slot and com plete the connections that connect the card to the
motherboard and its bus structure through the slot. As I will discuss later, the card and slot
have to be the same type of interface. Figure 11-2 shows a card being inserted into a slot.
Notice the card’s edge connectors and how they match u pto the ex pansion slot.Using Expansion Cards
Expansion cards were used to add basic functions to older PCs, including memory, hard
diskandfloppydiskcontrollers,videocontrollers,serialandparallelports,modems,and
even the clock and calendar functions. Today’s PCs add only a few of these functions
throughexpansioncardssincemostofthesecapabilitiesarebuiltintothemotherboardor
chipset.Typically,expansioncardsarenowusedtoimproveoraddtothecapabilitiesofa
PC, such as controllers and adapters for special purpose hardware and network inter-
faces.ThroughexpansioncardsaPCcanbecomeasoundsystem,agraphicsworkstation,
a movie theatre, or a member of a global network.Chapter 11: Expansion Cards^221
Figure 11-2. An expansion card and an expansion slot on a motherboard