A method and apparatus to scrub a memory during a scrub period, of a computer system. The computer system has a memory controller that receives read requests and write requests from a processor. The memory controller provides a different priority for scrub requests versus read requests during a period of relatively light memory workload versus a period of relatively heavy workload. The memory controller provides a relatively higher priority for scrub requests near an end of a scrub period if scrub progress is behind an expected scrub progress.