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The Power Mac G5 Quad: Seat belt not included!

Apple's latest desktop machine offers exponential increases in speed

By Yuval Kossovsky
November 16, 2005 12:00 PM ET

Computerworld - NEW YORK -- Yesterday, I had an hour to work with Apple Computer Inc.'s new Power Mac Quad G5, and for anyone in the broadcast, sciences, music, print and photography industries, I have some advice: Place your orders now!

The latest Power Mac, unveiled last month and now shipping in limited quantities (see "Update: Apple unveils dual-core Power Mac, revised PowerBooks"), offers substantial architecture improvements over its predecessor that deliver exponential performance increases -- depending on the application being used or function performed. In addition to the use of dual dual-core G5 processors, the underlying upgrades are numerous, so I'll just list them here and then offer some commentary.

The dual-core technology now used in the $3,299 top-end Power Mac G5 puts two processors on one silicon wafer, with each processor allocated 1MB of L2 cache. The result is twice the computing power in the same space. In a dual-processor, dual-core, machine (Apple refers to it as a quad-processor machine, although others call it a dual-dual), you've got four processors, four 128-bit velocity engines and eight graphics processing units. The speed increase on any computing work that can be broken up into parallel processing is exponential.

Real-world performance throttles back a bit due to disk I/O, but the increase in speed is immediately noticeable. I witnessed Final Cut Pro effects applied in real-time to eight video streams, and performance was barely affected. It must have something to do with the total RAM throughput being 8.5GB per/sec. It's also worth noting that Mac OS X 10.4 and the G5 architecture can support up to 4TB of RAM. The machine isn't built to hold that much, since 99.9% of the user base couldn't afford it, but if you fill the 533-Mhz Double Data Rate 2 RAM Error Correction Code slots with the full 16GB on memory the box can currently hold, you've still got quite a screamer.

PCI Express Bus
The Power Mac G5 now supports PCI Express. Each processor core has direct access to the front-side bus controller, and the new architecture supports 16, 250MB per/sec. lanes for a total throughput of 4GB per/sec. -- almost twice as fast as a 133MHz PCI-X slot. There are 150 watts of power in the bus, enabling current and future high-end display cards to operate at peak performance. In addition to the 16-lane graphics slot, the Power Mac G5 features three PCI Express expansion slots: two four-lane slots and one eight-lane slot. You can install a PCI-Express graphics card in any PCI Express slot, allowing a single Power Mac

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