Long exposure noise is related to thermal implementation - specifically, how fast can they get heat away from the sensor's general physical vicinity. Since none of us have any idea of what the D800 board's layout is, or which of its components generates the heat, it's a sure thing that we don't know how well it will perform in this regard.
Two things to illustrate why we can't tell would be (a) the fact that this is engineered to do video, which generates a LOT more heat than typical still work, and (b) everything in this camera is running at a higher clock rate than in past machines, due to the data rates involved. For the CMOS stuff that is probably in use in this camera, thermal consumption is dependent on clock rate, meaning that at least the data transfer pipeline if not also the processing pipeline are likely to produce more heat than past implementations. On the other hand, they may also run at lower voltage...
_____ Brian... a bicoastal Nikonian and Team Member
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