A question about task's select delay alternative

[NiGHTS <nights@unku.us>]

In a task with a select like this...

task body X is
begin
    loop
        select
            accept Y;
        or
            delay 10.0;
            exit;
        end select;
    end loop;
end X;

What does "delay" actually do to the CPU? In this case I am using the Adacore GNAT compiler for a PC. Is it a loop constantly evaluating elapsed time? Or is it some kind of timed interrupt?

Thanks for your feedback!