Bare Feats has posted results from several benchmark tests
between a stock Dual Core 2.5 Ghz PowerMac G5 and a stock Single Core Dual 2.5 Ghz PowerMac G5 - even though they don't actually have one of the new machines in hand yet. The tests were apparently done by "multiple independent sources" and are assured to be reliable. Either way, the results more or less live up to what I bet most would imagine: the Quad Core hauls some serious cycles.
The Quad Core machine performs a NightFlight Render nearly twice as fast as the Dual G5, and the Quad Core also performed a series of multi-processor optimized Photoshop CS2 filters filters in 17.6 seconds, while the Dual G5 took 25.8. Check out the full list
of test results for more details including Cinebench, Xbench and UT2004 tests. Afterwards, you may re-commence drooling.
[via Inside Mac Games