As described in Differentiating Reality and Knowledge of Reality there are simply two different ways to gain knowledge about physical reality. Objective observation from afar is necessarily abstract and substrate independent. A dictionary or transducing system is required to preserve the meaning across diverse representations. No dictionary is required for actual physical qualities, so it is more efficient, the same way as software running directly on hardware is more efficient than on a virtual machine. Abstract CPUs use discrete logic to do computational binding on different representations of information, sequentially. Consciousness does computation in a fundamentally different parallel way.
Conscious knowledge is the final result of perception. Our perception system renders our conscious knowledge into the CPU of our brain. We directly apprehend the physical qualities that have been rendered into our brain’s CPU as a meaningful composite experience. There must be some physical process which achieves this phenomenal computational binding which enables us to have composite qualitative situational awareness. Our ability to directly apprehend multiple physical qualities as a composite conscious experience is the key to our ability to do phenomenally conscious computation.
Consciousness is what it is like for a large parallel processing CPU to compute directly on physical qualities.