Apple Power Mac G5 - Manual (Page 11)

AGP 8X Pro Graphics Bus
The Power Mac G5 integrates the latest graphics interface, AGP 8X Pro, for next-
generation gaming and advanced graphics production. Compared with the AGP 4X
interface in previous Power Mac systems, the new specification doubles the maximum
transfer rate and doubles the amount of data transferred in a single AGP bus cycle.
The 32-bit, 66MHz AGP 8X Pro bus strobes eight times per clock cycle, resulting in a
533MHz data rate and a maximum bandwidth of 2.1 GBps. This increased performance
enables graphics-intensive applications to achieve higher resolutions with improved
complexity and texturing, for a more immersive visual experience.
The “Pro” component of the new AGP specification is designed to deliver additional
electrical power to the graphics card. The Power Mac G5 uses High Power AGP,
delivering 75 watts to support advanced, higher-powered graphics cards, such as
the optional ATI Radeon 9800 Pro.
133MHz PCI-X Expansion
The Power Mac G5 introduces Macintosh users to PCI-X. This advanced expansion
protocol addresses the need for higher-performance PCI devices, increasing the
speed from 33MHz to 133MHz and throughput from 266 MBps to 2 GBps. PCI-X also
operates more efficiently than PCI, resulting in more usable bandwidth at any clock
frequency—ideal for high-bandwidth applications. The PCI-X specification uses 3.3V
signaling and is designed for compatibility with legacy 3.3V and Universal cards.
5
High-Performance I/O
The Power Mac G5 architecture uses the HyperTransport protocol to integrate the I/O
subsystems and connect them to the system controller. Serial ATA, Gigabit Ethernet,
FireWire, USB 2.0, optical digital audio, and analog audio are all integrated through
two bidirectional 800MHz HyperTransport interconnects for a maximum throughput
of 1.6 GBps.
For more information about the many expansion and I/O options available on the
Power Mac G5, see the section “Leading-Edge Expansion.”
Serial ATA Storage
Serial ATA is the next-generation industry-standard storage interface, replacing the
Parallel ATA interface. Designed to keep pace with the demands of digital video
creation and editing, audio storage and playback, and other data-intensive applica-
tions, Serial ATA supports 1.5-Gbps throughput per channel (equivalent to a data rate
of 150 MBps).
The Power Mac G5 can hold two internal Serial ATA drives for a total capacity of up
to 500GB of storage.
3 Each drive is on an independent bus, so there’s no competition
for drive performance as with Parallel ATA. Performance is improved even further
when drives are striped using software RAID in Mac OS X.
11 Technology and
Performance Overview
Power Mac G5
Parallel ATA
100 MBps
Hard Drive
Hard Drive
Serial ATA
150 MBps
150 MBps
Hard Drive
Hard Drive
2000
133
0
1000
2000
266
Megab
y
te
s per sec
ond (MBps)
Power Mac G5
PCI-X (64-bit,
133MHz)
Power Mac G4
PCI (64-bit,
33MHz)
Standard Pentium
4–based system
PCI (32-bit, 33MHz)
PCI-X versus PCI
The Power Mac G5 with PCI-X slots provides
bandwidth of up to 2 GBps for PCI devices,
eight times more than a Power Mac G4
and sixteen times more than a Pentium
4–based system.
Serial ATA versus Parallel ATA
The Power Mac G5 features two internal
Serial ATA drives, each on an independent
bus—so there is no competition for drive
performance, as with Parallel ATA.