[I'm made a separate posting of my answer to this.]
What is uploading?
Uploading (sometimes called "mind uploading") is the hypothetical process of transferring a mind from a biological brain to a computer.
The idea is that by scanning the synaptic structure of a brain, we could implement the same computations on a computer that would normally take place in the brain. If you think the essence of yourself is information -- your memories, values, attitudes and emotions -- rather than the grey, cheesy lump inside your skull, then you might view your identity as being preserved in this process. The scanning could be accomplished by means of nanotechnology.
Uploading should work for cryonics patients provided their brains are frozen in a sufficiently intact state.
Uploads could live in an artificial reality (i.e. constructed computer-simulated environment). An option would be to have robot bodies and sensors so they can resume their lives in physical reality.
The subjective time of uploads would depend on how fast the computers are on which they are running.
Uploads could be distributed over vast computer networks and they could make frequent backup copies of themselves. This should make it possible for uploads indefinite life spans.
Uploads could subsist on a very small amount of resources compared to a biological human, since they don't need physical food or shelter or transportation.
Uploads could reproduce extremely quickly (simply by making copies of themselves). This implies that resources could quickly become scarce unless reproduction is limited.
What is the singularity?