If you use Connect-X host bus adapters from Mellanox Technologies for your Ethernet or InfiniBand networks and you use Linux, then there's a turbo boost mode available for $300 per server. The software used to be called Voltaire Messaging Accelerator and came to Mellanox through its November 2010 acquisition of networking rival …
It's just the code for the TCP/IP stack down to the Network Card taken out from the Kernel and compiled and provided as a User Mode library to avoid User to Kernel context switches?
Sound like it, just like Solarfare's Open Onload.
From http://www.openonload.org/ it seems like OpenOnload is purely software solution (IP stack implemented in userspace), whilst Mellanox claim to fame is "user space Linux library that offloads the processing associated with TCP, UDP Multicast, and UDP unicast traffic to the adapter card" which I understand means parts of IP stack are executed in actual hardware (embedded chip on the card). This would explain difference in latencies : OpenOnload claims something above 3us, Mellanox under 2us which is quite nice :)
OpenOnload works with Solarflare NICs, so its a mixture of the hardware and software.