Comment by anon291

of course it has a read write head. In fact it has N read / write heads equal to the size of the context since each latent state is updated with the results of the cross attention mechanism at each step.

Alternatively, you can view the '<unknown>' token that is dynamically driven to the embedding of the output token to be the write head. Either way, the simple truth is that you can train a transformer system (i.e., an iteratively applied transformer) to simulate an arbitrary turing machine.