Modems and adapter cards for video, TV, sound, network cabling, disk drives, and tape drives generally take the form of circuit boards, or cards, that you install inside your PC’s case. These slots are connected to your PC’s bus, an electrical conduit that connects all the components of the machine to the brains of the outfit: the processor and memory.
The two common (and incompatible) kinds of slots are called PCI and PCI Express (PCIe). The PCI slot (Peripheral Component Interconnect) has been around since the dawn of the PC in the early 1990s. PCI Express is newer and offers much better speed but is typically used only for graphics cards. Most computers in use today have both kinds of slots.
There’s a third type of slot in some computers, called AGP (Accelerated Graphics Port). This slot is almost always occupied by a graphics card. PCIe is the most popular slot type for graphics cards, but you may encounter AGP in older PCs.
Knowing the characteristics of the different bus types isn’t especially important. What is important is knowing what type of slots your computer has free, so you can purchase the correct type of expansion card. To do this, you’ll have to open your PC’s case to see which type of slots are empty:
PCIe slots come in different lengths, depending on their speed (from x1, the slowest, to x16, the fastest and most common). They have metal pins or teeth in the center and a small crossbar partway down the slot. There’s also a slot ...