g-5 2005 or 2006 is dual core intel
From Apple's Support Article:

Mac OS X v10.6 Snow Leopard system requirements

To install Snow Leopard for the first time, you must have a Mac with:


An Intel processor
An internal or external DVD drive, or DVD or CD Sharing
At least 1 GB of RAM (additional RAM is recommended)
A built-in display or a display connected to an Apple-supplied video card supported by your computer
At least 5 GB of disk space available, or 7 GB of disk space if you install the developer tools