(^308) PC Hardware: A Beginner’s Guide
Plug and Pray
AcommonproblemwithPCsisthatusersassumethateverythingisPlugandPlay(PnP)and
that PnP is an infallible system—wrong on both counts. In order for a PC to support PnP at all,
it must have PnP support from the motherboard, the chipset, the processor, the operating
system, and the device itself. Virtually all PCI cards are PnP compatible, but only if the other
components of the PC are also PnP compatible. The second problem with PnP is that it can
cause resource conflicts if the resources the device is expecting to use are already in use.One Step at a Time
When installing new devices in the PC that require system resources (that is, virtually ev-
ery device), install one device at a time and then test the system. Don’t install several new
devices and then try to figure out which one may be causing a resource conflict. It is much
easier to debug if you add each device in a completely separate installation process.Read the Fantastic Manual (RTFM)
I am a firm believer in reading the documentation that comes with a device or compo-
nent, especially the parts that deal with installation or troubleshooting. Often there is a
ready remedy available to the problem caused by the device. In the worst case, the tele-
phonenumberoftheirtechnicalsupportdeskisusuallyincludedinthedocumentation.Troubleshooting IRQs
In the beginning, PCs had only 8 IRQs. When the second grou pof 8 IRQs was added, the
two groups were linked through IRQs 2 (on the lower group) and 9 (on the upper group).
Video cards and other devices are sometimes assigned to IRQ 2, which means that they
will conflict with anything installed on IRQ 9.
IftwodevicesareinstalledtothesameIRQandtheywillnotbeusedatthesametime,
such as a modem and a NIC (although that is a really strange pair of devices to share an
IRQ), there should be no problem. However, more commonly you may find that you
have installed devices on both COM2 (like a modem) and COM4 (like a serial mouse) and
they cannot operate at the same time. This is especially common on legacy systems on
which a device is installed using proprietary installation software.
About the only problem you can experience with IRQs is that two devices have been
assigned to the same IRQ. The solution is to reassign one of the devices to a new IRQ us-
ing the Device Manager, the BIOS settings, or by changing the card’s jumper or DIP
switch values.