Machinery can be a lot simpler than biology. Birds are incredibly complex systems: wing structure, musculature, feathers, etc. An airplane can be a vaguely wing-shaped piece of metal and a pulse jet. It doesn’t seem super implausible that there is some algorithm that is to human consciousness what a pulse jet with wings is to a bird. Maybe LLMs are that, but maybe they’re far more than is really needed because we don’t yet know what we are doing.

I would bet against it being possible to implement consciousness on a PDP, but I wouldn’t be very confident about it.