In order to run the test bench, two additional packages are required
vlog_tb_utils : Adds support for generating VCD files and being able
                to abort simulation after a set time
wb_bfm        : Wishbone Bus Functional Model that generates wishbone
                write/read requests to wb_sdram_ctrl and checks that
                the correct data is read back after a write

Both these packages are available from github.com/openrisc/orpsoc-cores