The key to any computer's hardware success is expandability. The old Apple computer triumphed over its peers in the late 1970s because the Apple II could be expanded; inside the computer's case was a row of expansion slots. Into those slots, users could plug expansion cards, which greatly increased the computer's capabilities.
The first IBM PC also had expansion slots, which helped ensure its success. And, though the early Macs lacked expansion slots, pressure from users eventually won Apple over, and the top-of-the-line Mac models sport expansion slots for power users who want them. (The iMac doesn't have expansion slots.)
Why you may need expansion slots
Expansion slots allow you to add new options or features to those that come with a standard computer. The slots aren't as necessary as they were in the past; early IBM PCs lacked such luxurious features as video adapters, serial ports, and even extra memory. You could add all that by plugging in the proper expansion cards.
Computers now often come with everything you need. For example, the iMac has an internal modem and a network adapter and room for more memory. Any further expansion can be added via the USB or FireWire ports. Some power users may want more than that, though, so other computers come with expansion slots.
- Expansion slots increase the flexibility of your computer system and ensure that you can upgrade and improve your system in the years to come.
- Some low-end home computers or all-in-one systems, like the iMac, are designed for people who need basic computers and, therefore, probably don't need expansion slots. If you need expansion slots, however, steer clear of those systems.
- If you want to add a network card, a second monitor or video adapter, a satellite modem, a FireWire adapter, a port, an improved sound card, or any of a number of options, your computer needs expansion slots.
Types of expansion slots
As with everything else, a computer can't have just one typical expansion slot. Most computers have several different types of expansion slots inside their boxes. Sure, some are better than others. Still, a mixture of several types is generally preferred. Here are the popular ones:
- PCI: This type of expansion slot is the most popular one on both the G5 Macintosh and the PC. The PCI expansion slot connects directly to the computer's microprocessor, which makes it very fast. It stands for Peripheral Component Interconnect.
- AGP: A special slot designed specifically for video adapters is the Accelerated Graphics Port, or AGP, slot. Although PCI video adapters are available, if your computer has an AGP port, you're better off buying and using an AGP video adapter.
- ISA: The original slot found on the first IBM PC is still around, mostly because ISA expansion cards are still with us. ISA stands for Industry Standard Architecture.
Which type of expansion slots should you have? If you want a computer with plenty of expansion slots, you may want to have three to five (or more) PCI slots. PCs (not Macs) may also have one or two ISA slots for backward compatibility (though they're optional). And, having an AGP slot is nice if you want to use the latest, greatest video adapters (on the PC).
- Computer memory once plugged into expansion cards. Computers are now designed so that their memory chips plug directly into the computer's main circuitry.
- Some PCI expansion cards can even be used in either a PC or a Mac. Be aware that some PCI cards are Mac- or PC-only.
- Computer scientist types refer to the expansion slots as the bus, so they use the term PCI bus rather than PCI slot.
