Method of generating a random binary number using gates
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Uncertain Circuits: When transistor 1 and transistor 2 are switched on, a coupled pair of inverters force Node A and Node B into the same state [left]. When the clock pulse rises [yellow, right], these transistors are turned off. Initially the output of both inverters falls into an indeterminate state, but random thermal noise within the inverters soon jostles one node into the logical 1 state and the other goes to logical 0.

Also see the white paper (Respawned Fluff note: This is for an older Intel method, using two free-running oscillators, not the one described above.)