Using Additional Buses

Mac OS X supports several other buses for connecting a wide variety of peripherals, including video cards, audio cards, and internal and external hard drives.

PCI and PCI-X

Peripheral Component Interconnect (PCI) cards are expansion cards that are installed inside desktop computers after turning off power. Because of their very high throughput compared to the plug-and-play connection buses, PCI cards are often used to add display capabilities, hardware RAID, or high-end analog video capture and compression. PCI cards are available to add a SCSI bus as well as additional USB and FireWire buses. PCI supports bus speeds up to 66 MHz, and PCI-X supports bus speeds up to 133 MHz. Note that PCI buses are present even in Macintosh models that lack slots, such as the iBook and PowerBook.

AGP

Accelerated Graphics Port (AGP) is a standard video card connection bus used by many graphics card manufacturers. It is a faster connection bus than PCI, making it ideal for high-performance video. Current Power Mac G5 computers have an 8x AGP Pro slot for the primary video card.

PC Card

Also known as CardBus or PCMCIA (Personal Computer Memory Card International Association), the PC Card bus is used primarily on laptop systems. The thickness of PC Cards is indicated as Type I, Type II, or Type III. Although support for PC Cards was included in Mac OS 9, the use of PC Cards in Mac OS X requires a version higher than 10.0.3.

ATA and Serial ATA

Advanced Technology Attachment (ATA), also referred to as Parallel ATA, is an internal bus used to connect storage devices, such as hard disks and CD-ROM drives. Most Mac OS Xcompatible computers prior to the Power Mac G5 incorporated ATA buses for internal storage and optical drives. As ATA performance has improved, other names have appeared for ATA connections, which describe ATA bus speeds such as "ATA-100." All ATA buses are built on the Parallel ATA protocol.

Serial ATA is the next-generation industry-standard storage interface that replaces the standard ATA interface for the hard drives in the Power Mac G5. Serial ATA supports 1.5 Gbit/s throughput (equivalent to a 150 MB/s data rate). Since each Serial ATA drive is on an independent bus, there's no competition for bandwidth as with Parallel ATA.

Macintosh computers that ship with Serial ATA buses include an ATA bus to connect slower storage devices such as optical media drives.

SCSI

Small Computer System Interface (SCSI) is a high-speed bus used mostly for storage devices. Due to the comparatively higher cost of SCSI drives and interfaces, ATA drives are used more commonly for internal storage. SCSI bus devices usually are reserved for systems that require high-performance data transfer. Current Macintosh systems do not have SCSI built in, and they require the addition of a PCI card to connect SCSI devices.