"the Vls speed (lowest selectable speed- V ref) which is displayed as an amber line, is computed by the flight augmentation computer according to the AofA sensors."
That's the crucial part. How exactly does the FAC in your bus convert AoA to speed? In other words, how does the FAC determine your stall speed independent of the FMC data. On my current aircraft, the FMC doesn't send that information to any other systems.
PS. Why can't pprune have a QUOTE button like every other forum?