Addendum:

> the southbridge, which is rumoured to be the AMD SB600.

Seems the rumour was spot on. Compare:

http://amigaworld.net/modules/newbb/viewtopic.php?topic_id=31514&forum=33&start=80#557201 (1st link therein)

vs.

http://img.tomshardware.com/us/2008/03/04/amd_780g_chipset/amd_780g___sb600.jpg