It's not different from eval $1 at all. Because it is eval $1.

However, by the time that $1 has been passed, the Lisp zeroes and ones of the eval function have been turned into the appropriate machine language of the CPU.

As of course different CPUs have different evaluation pipelines for integers, floats, vertices, branches etc.

So it evaluates a block of lisp as purely integers, floats, branches, vertices, and sends the appropriate data type off to the appropriate evaluation line, and reassembles it.