So then what the hell is it doing, if it's not completing a double SHA256? You've completely lost me on this. Again I have to ask... if it's not completing a double SHA how does it know that it's got any valid hash below the target?
You don't need the last few steps in sha to examine the first few bytes.
So the ASIC is essentially "screening"
POSSIBLE candidates for a solution? It rapidly discards impossible solutions and only alerts the upper level processor when it "might be onto something"?