We mentioned in our earlier article on motherboards that modern motherboards can have most of the functionality needed integrated into the on-board electronics, such as modems, networks cards, graphics cards, etc. While this is certainly true, many PCs use motherboards that do not have this functionality integrated. So what happens if you decide to use your PC on a home network but find that there is no network interface built into the PC? The answer is that you fit a network interface card to one of the empty PCI slots on your motherboard (refer back to the motherboard article to see what these slots look like). The PCI slots in motherboards allow plug-in cards to be inserted and these can then communicate with the rest of the PC. In order for this to happen device drivers must be installed, but we'll come back to them in a moment.
The picture on the left shows a variety of different plug-in cards that can be added to the motherboard to enhance the functionality of the PC. From the top down we have a modem card, a graphics card, a sound card and a 10/100 network interface card. With the exception of the graphics card, these all can be fitted to any free PCI slot on the motherboard (most motherboards have between 3 and 5 PCI slots). The graphics card is plugged into a special dedicated graphics slot called the AGP (advanced graphics port) slot, of which there is ever only one on a motherboard. Other PCI slot plug-in cards that could be fitted include TV tuner cards, USB connector cards, wireless network cards and Firewire cards. As there are a limited number of PCI slots on your motherboard, and some of them may already be occupied, you may not be able to fit all of the options just listed.
If you bought your PC in the last 12 months you may have a new type of PCI slot called a PCI Express slot in addition to, or instead of, standard PCI slots. These new slots use a different architecture which allows data to transfer at significantly higher rates than the older PCI slots and will eventually replace the older slots on all new motherboards. The PCI and PCI Express slots are a different physical design and cards designed for one slot type cannot be used on the other.
Just inserting a plug-in card in a slot is not enough to allow the card to start operating with the rest of the hardware and the operating system. In order to get the card talking to the other hardware and the OS it is usually necessary to install what are known as device drivers. A device driver is a software program written for a specific piece of hardware that allows it to communicate with the rest of the system. Drivers can sometimes become corrupted and when that happens the hardware that the driver was written for can malfunction. This can normally be remedied by the removal of the corrupted driver followed by a reinstall of the driver. Often manufacturers of plug-in cards release their products to market before their drivers have been fully debugged and problems can arise when using the hardware under certain situations. Because of this it is not uncommon for the manufacturers to release updated drivers that address known issues as they come to light. Windows XP makes it easy to update drivers as new versions are released.
Of all the various types of plug-in cards that are available, adding or upgrading a graphics card is probably the commonest, particularly if a PC is being used for playing games. When it comes to adding a new graphics card, the sky is the limit in terms of how much you can spend. The card on the left is a recently released XFX GeForce 7900GTX graphics card for playing the latest and next generation of games. This will set you back a cool €650 - more than you might pay for a new PC system from Dell. For the dedicated gamer only!
Next up, optical drives.