What is 'SBUS' (connecting 2 Macs together via 2 Symphony64 cards) and is it still supported?

SBUS was a functionality that was included with the original Symphony 64 PCIe release.  SBUS let you connect multiple Macs together to pass audio back and forth between them using Symphony 64 PCIe cards.

Unfortunately, it was no longer supported after the release of Symphony I/O (original Mk1 version).

To use SBUS, you need at least 2 Macs (each Mac must be running OS version 10.5.8 or 10.6.8) and 2 Symphony 64 cards, along with at least one compatible Legacy Apogee converter (AD16x, DA16x, Rosetta800, or Rosetta200).