CPU usage drops to 15% to 18% When rendering video

[Naymul Haque]

A 4 mintues video is taking more than 9 hours to render. Initially the Encoder was using 90% to 100% of the cpu and rendering was going fast. But suddenly after 5 to 10 minutes, the CPU usage dropped to 10% to 18% and rendering became a nightmare. Any idea why this happened suddenly? 

Video format: H.264, 1920x1080, VBR Pass 1, 

PC Spec: Ryzen 7 5800H, 16gb Ram, RTX 3050 laptop gpu

[Peru Bob]

What are the hard drives (how many, what kind, what is on each, what capacity, and how full)?

[Naymul Haque]

My laptop has a 500gb NVME Gen 3 SSD and it was around 80gb free during the render.

[Peru Bob]

Depending upon the effects and transitions used, that may or may not be enough free space.

[Naymul Haque · Accepted solution]

It was probably THERMAL THROTTLING on the CPU. The video was rendered within 30 minutes after I turned off the PC  and turned it on for a few minutes.

[Peru Bob]

Thank you for posting the solution so that others might benefit from it.