Can you explain why this has significant performance improvement on my windows 10 workstation? is the chip in the card taking load off the main cpu?

Thanks for asking. This card equipped with the original Intel 82576 controller chip which improves performance and throughput by reducing the I/O overhead, and it provides near-native performance, data protection, and enhanced support for pass-through traffic to the board management controller. Meanwhile, it supports Intelligent Offloads and makes the servers more stable. Same as Intel E1G42ET PICE Card. So this card has significant performance improvement on Windows 10 workstation.