Apple Power Mac G5 (Late 2005) - Manual (Page 11)

11 Technology Overview
Power Mac G5
533MHz DDR2 Main Memory
The new 128-bit memory controller in the Power Mac G5 supports DDR2 main memory
running at speeds up to 533MHz. In addition to writing data at a double rate, or twice
the rate of the clock speed, the memory controller increases e∑
ciency by reordering
read and write operations. By addressing two banks of SDRAM at the same time, the
new Power Mac G5 can reach a memory throughput of up to 8.5 GBps. That represents
a 25 percent increase over the latest Power Mac G5 and triple the throughput of the
fastest Power Mac G4.
With its 64-bit processor architecture, the Power Mac G5 can address more memory
than any previous Macintosh and many desktop PCs. All Power Mac G5 systems can
hold up to eight 2GB DIMMs for up to 16GB of memory. For users in mission-critical and
compute-intensive environments, there’s also the option of ECC (Error Correction Code)
main memory, which allows automatic correction of single-bit errors and detection of
multiple-bit errors.
This high-speed, high-capacity memory architecture enables graphics, video, audio,
and scientifi c applications to run radically faster. Enormous fi les and data sets can be
loaded into RAM for rapid access by the PowerPC G5—without having to access system
storage. Data can be retrieved from memory 40 times faster than from the hard drive.
In fact, accessing the fi rst critical word of data from memory is 60,000 times faster
than from a hard drive, so manipulation and analysis of data can be performed at
remarkable speeds.
PCI Express Graphics
With the introduction of PCI Express architecture comes a new 16-lane PCI Express
graphics interface that supports the latest graphics controllers and delivers up to
4 GBps of data throughput. By supplying up to 150 watts of power to the primary
graphics processing unit, the new Power Mac G5 provides the headroom for high-
performance, next-generation graphics processors and applications, enabling even
higher resolutions for stunning realism.
For more information about graphics cards, Apple displays, and graphics technologies,
see the “Workstation Graphics” section.
PCI Express Expansion
The all-new PCI Express architecture allows you to customize your Power Mac G5 to
the needs of your workfl ow—providing tremendous power and productivity in a single
system. As your needs change, you’ll have the fl exibility to add solutions for emerging
workfl ow scenarios, such as HD video and next-generation networking.
Modern serial expansion architecture
PCI Express is a modern industry standard sponsored by the Peripheral Component
Interconnect Special Interest Group (PCI SIG). Because older parallel technologies
placed multiple devices on a single bus, the slowest device determined the speed
of the entire bus. A serial technology, PCI Express guarantees each device dedicated
bandwidth to and from the system controller.
PCI Express communicates in 250-MBps “data lanes.” PCI Express cards and slots are
defi ned by their bandwidth, or number of data lanes—typically one lane, four lanes,
eight lanes, or 16 lanes. At 250 MBps per lane, a four-lane slot can transfer data at
up to 1 GBps and an eight-lane slot, up to 2 GBps—approximately twice as fast as a
133MHz PCI-X slot.
Up to 25 percent faster
memory throughput
With support for DDR2 memory, data
throughput on the new Power Mac G5
is 25 percent faster than previous Power
Mac G5 models and up to three times
faster than the Power Mac G4.
6.4 GBps
2.7 GBps
128-bit DDR2
at 533MHz
8.5 GBps
128-bit DDR
at 400MHz
64-bit DDR
at 333MHz
Almost twice the graphics throughput
The 16-lane PCI Express graphics interface
increases throughput to up to 4 GBps,
almost double that of AGP 8X in previous
Power Mac G5 models.
2.1 GBps
16-lane
PCI Express 4 GBps
AGP 8X
Up to twice the PCI throughput
PCI Express delivers a radical increase in
throughput compared with the expansion
technologies on previous Power Mac G5
systems (PCI-X and PCI) and Power Mac G4
systems (PCI).
1 GBps
1 GBps
0.25 GBps
Eight-lane
PCI Express 2 GBps
Four-lane
PCI Express
PCI-X 64-bit,
133MHz
PCI 64-bit,
33MHz