g.f.
As you saw in that other post, the debugging was never concluded. There were layout issues that complicated the analysis. I requested an update on this design debug.
The C6678 does support 2 ranks of DDR3 memory. However it does not support mirrored addresses on the 2nd rank. This prevented testing of the second rank during device qualification since all dual-rank UDIMMs available at that time required address mirroring.
Twin-die devices are only recently becoming cost competitive. We do not know of any reason they should not work with the C6678 but we do not have a board with that configuration. We are planning some tests over the next few weeks using twin-die devices.
Tom