After upgraded to RouterOS v7, cpu-frequency is missing.
Only RB4011 hit this issue, other RouterBoards with RouterOS v7 works fine.
[admin@MikroTik] > sys resou pri
...
total-memory: 1024.0MiB
cpu: ARMv7
cpu-count: 4 # There should be "cpu-frequency" after this property.
cpu-load: 3%
free-hdd-space: 404.7MiB
total-hdd-space: 512.2MiB
architecture-name: arm
board-name: RB4011iGS+5HacQ2HnD
platform: MikroTik