Hot Swap
PC Cards are hot-swappable, which means they can be inserted and removed while the
system is running and do not require the system to be restarted to recognize the card. Not
all PC Card devices totally adhere to the PCMCIA specifications; these require a software
driver before they are fully functional.SCSI Interfaces
The SCSI (Small Computer System Interface) is not technically an expansion bus struc-
ture, but it can be used to add additional internal and external devices to a PC. Because
they are more expensive than comparable ISA or PCI devices, SCSI (pronounced
“skuzzy”) devices are usually found on network servers and high-end workstations and
not on home PCs.
SCSI adapters provide a very easy way to connect multiple (as many as 15) internal
and external devices on a single interface. These devices can be either inside or outside the
system case. SCSI, which is covered in detail in Chapter 9, has been around for some time
and has a variation to fit just about every system, including both ISA- and PCI-compatible
host adapter (expansion) cards.Serial and Parallel Ports
Serial and parallel ports have been on PCs from the beginning. Serial ports are usually
associated with communications and parallel ports with printing, but there are serial
printers and many peer-to-peer networks are connected over parallel ports.
On older PCs, such as PC XTs through and including most 486s, serial and parallel
ports were not included on the PC’s motherboard but were added through expansion
cards,whichwereinsertedprimarilyintoISAslots.Commonly,amultifunctioncardwas
used that added one parallel port and a 25-pin serial port. Daughterboards, inserted into
another slot and connected back to the main multifunction card by a twisted-pair cable,
were used to add still more serial or parallel ports to the system.
On today’s PCs, which rarely require more than one serial or parallel port, these ports are
mounted directly on the motherboard. Additional ports can be added through an expansion
card. See Chapter 19 for more information on these and other I/O ports and connectors.USB and IEEE 1394 Interfaces
Two newer interface standards that are used to connect external peripheral devices to a
PC are the USB (Universal Serial Bus) and the IEEE (International Electrical and Elec-
tronic Engineering) 1394 standards. The IEEE 1394 standard is more commonly known as
FireWire or by its generic name, the High Performance Serial Bus (HPSB). Both device
interfaces support low-speed devices like keyboards and mice as well as high-speed,
high-performance devices like video cameras, scanners, and printers. These interfaces
are hot-swappable and Plug-and-Play compatible, which means they can be added orChapter 11: Expansion Cards^229