Asus Republic of Gamers Thunderbolt Xonar Audio / Bigfoot Killer NIC-E2100 LAN PCI Express x1 Combo Card. Combining the best of technology, Xonar audio high performance and NPU (Network Processing Unit) dedicated in a single PCIe card, the Asus ROG ThunderBolt has been designed specifically for professional players. The Xonar is tuned for stereo earphones, while the NPU removes all network management CPU, which means that 100% of the system resources are dedicated to the game that is being played. Saved for better hardware ROG, is the latest addition to a system of professional games.