From what I've been reading several things are possible. A BIOS update to allow 13x+ multipliers. Re-mapping an unused (5x) multiplier to 13x. AMD may just hardware lock (where the L1 bridges do NOTHING) the chip to a 13x multiplier.
This would be like INtel with E and EB processors. Yes, it would suck but they've been saying this was coming all along.
Remember, in order for the 1.3 GHz to work in pre KT133-A chipsets, it MUST have a 13x multiplier!
Cheers!