Related to all of the people who've already sunk a bunch of work in to this; the official lore/backstory says that the whole premise was instigated by a Big/Little Endian mixup, and that the DCPU is supposed to be Little Endian...

But from Notch's spec document:

"Instructions are 1-3 words long and are fully defined by the first word. In a basic instruction, the lower four bits of the first word of the instruction are the opcode, and the remaining twelve bits are split into two six bit values, called a and b. a is always handled by the processor before b, and is the lower six bits. In bits (with the least significant being last), a basic instruction has the format: bbbbbbaaaaaaoooo"

In other words, the current DCPU spec is Big Endian. So I wonder if Notch will be rewriting the spec, even though from all accounts it seems that he's already implemented the emulator.