want to generate variable pulses up to 8 MHz. I tried NE555 but it only generates 500

want to generate variable pulses up to 8 MHz. I tried NE555 but it only generates 500KHz. any suggestions?
I need just IC or Micro controller number not device. It should have variable pulse generating capabilities and IC better over micro controller.

You don't mention duty cycle. How about a **broken link removed**?