removed from a PC without the need for rebooting or proprietary installation proce-
dures. Windows 98/2000 directly supports USB and IEEE 1394.
The basic difference between these two interface standards is speed, with IEEE 1394
providing better data transfer speeds and protocols. A new USB standard, USB 2.0, has
closed the ga psomewhat, but FireWire is still a better interface for real-time devices and
high-definition graphics.
USB devices can be connected to external USB hubs that can be daisy-chained together
to the point of 127 devices on a single USB bus. This means 127 devices are sharing not
only one bus, but one set of system resources as well. Figure 11-10 shows a USB port and
connector on the back of a PC. The USB port shown in Figure 11-10 is mounted directly on
the motherboard, but on many PCs, a USB or IEEE 1394 port must be added through an
expansion card.
IEEE 1394 is a slightly faster interface designed to support the bandwidth and data
transfer speeds of devices requiring an isochronous (real-time) interface. The 1394 interface
supports up to 63 devices that can have different device transfer speeds on a single bus.Expansion Cards
AsthePCadvances,moreandmoreofthedevices,controllers,andadaptersthatusedtobe
added to the PC via expansion cards are incorporated onto the motherboard. Many of the
functions that once required a separate adapter or controller card are now built into the
chipsetortheSuperI/Ochip(seeChapter5formoreinformationonchipsets).Thefollowing
sections review the common expansion card types.(^230) PC Hardware: A Beginner’s Guide
Figure 11-10. A USB port and connector on a PC