Software Issues for High Performance
Network card needed in user space. Myrinet is in user space; Fast Ethernet is in kernel
Interrupts (signals) are slow (15 microsec) Some applications can poll for incoming packets
Reliable multicast often needed. Let the Myrinet adaptor handle this itself
In general, a lot of software is tuned for slow networks (10 Mbps Ethernet, not 2.6 Gbps Myrinet)