Other World Computing has announced support for 1.5 GHz for the Mercury Extreme G4 upgrades. The Mercury upgrades are designed for boosting system processing speeds by replacing the G4 processor. The upgrades feature a pre-attatched heat sink and plug-and-play functionality. According to Other World Computing:
Other World Computing (OWC) today announced that the top-end model of its Mercury Extreme G4 processor upgrade line now supplies up to 1.5 Gigahertz (GHz) of plug-and-play performance to PowerMac G4 models.
A simple replacement upgrade for older, slower processors, the Mercury Extreme G4 line features Tantalum-dipped components and an ultra-quiet custom cooling system with a pre-attached heat-sink and fan in order to maximize the reliability and longevity of the upgrade.
You can find more information about the Mercury Extreme G4 upgrades at the Other World Computing Web site. The Mercury Elite Pro line is available starting at US$199.99 for the 700 MHz version.