Its a different principle to cpus, each brain cell does one operation (cycle) and the brain has 1 billion of them, so its like having 1 billion 1 hz processors. Also, human brains do not work on binary, they have 5 different chemicals to signal with so you could say its 0 to 4 binary instead of 0 and 1 which means they could do more than one operation as a cpu would and handle more complex operations so you could say
5 billion HRz
Also, someone researched that the brain can not miss a cycle (like system idea process in task manager) so the brain has a similar cycle running in your background (unconcious!) processes