How is the mvXCell-8i card "seen" from the PC side? As a standard PCI Express device?
A Linux PC sees the mvXCell-8i as an "Axon Companion device" on the bus. A special kernel module (called "axon") on the PC lets the PC and mvXCell-8i card share memory i.e. the PC can access a block of "remote" memory that is really "local" memory on the mvXCell-8i card. This module also allows transfer per DMA (not using either CPU) between mvXCell-8i and the PC. There is a special IBM framework (called Hybrid DaCs) which can use the DMA mechanism to pass data between the systems. For Linux a second special kernel module makes use of the axon module to create a virtual ethernet port via PCIe. This port can be used just like eth0 and is approx. 4 times faster than a Gigabit ethernet connection. It is only active once the mvXCell-8i card has booted.