PMS recommends a CPU with a passmark score of 2000 for a 10 Mbps video so an 80 Mbps video would need a score of 16,000. This is also assuming you are referring to H264 video. H265 takes a lot more power, so consider at least double the score needed if it is H265.
PMS when transcoding runs at 100% cpu load for the first minute to build up a buffer, so looking at the first minute is not a good indicator of the cpu usage needed. Either look later or check the server log itself for the “speed=” value.
