Low CPU usage

[CloroxBleach57]

I have pretty low CPU usage while rendering video in Blender. About 30% on all cores. How can I find out what might be bottlenecking my system? I'm guessing HDD or RAM but I don't know.

 

CPU: i7-3770

PSU: EVGA 650 watt

GPU: Gigabyte 5600 XT

Motherboard: Dell, unknown

RAM: 12GB ddr3 (2x4+2x2)

Drive: Old 1TB Seagate HDD

 

[SupaKomputa]

Probably it uses GPU more than the CPU.