If you are having issues with the beta firmware (0.98.1) with the last two dies not turning on, the solution is to heat the chip up to at least 60C.  Once you get up into the 60s, the last two dies will turn on.  Several people have confirmed this.  I turn off the heatsink fans, block the airflow from the front fans until the heat gets up to 60+, then I allow the front fans to run while leaving the heatsink fans turned off.  If temps drop back below 60C, the dies will turn off.