Comment Sure (Score 2) 133
Look up "Shadowplay" by nVidia. That is their software that uses the "nvenc" feature of their new GPUs. It has near zero CPU and GPU load, just load on the disk. All encoding is done by a special dedicated encoder on the chip. It's a fast encoder too, it can do 2560x1600@60fps.
The downside is it is not as good looking per bit as some of the software encoders (particularly X264) so if the target is something low bitrate you may wish to capture high bitrate and then reencode to a lower bitrate with other software later.
Bandicam also claims to support the hardware encoders of all the platform (Intel calls their QuickSync, AMD calls there's AMD APP).