3GIO means "third-generation I/O" - it was the original name for Intel's new technology which aims to replace today's PCI and PCI-X standards by 2003 or so. Nowadays, 3GIO is called Arapahoe. See the Arapahoe node for more detailed information.
Update:
3GIO/
Arapahoe has been re-named
PCI Express since I originally noded this. Not replacing PCI just
yet, though. There's no
PCI Express node at the time of this writing, so interested parties would be well advised to
Google.