The Giga Processor Card, GPC, provides the computational horsepower for the real time simulation. The component models, network solution, etc. are all solved on GPC processor cards.
As many as six GPC cards can be installed in one rack. Typically, one processor per rack will be dedicated to solving the network solution while others solve component models. The different processor cards can communicate with one another via the rack backplane; or alternatively, they can be linked directly via optical fibre. In addition to calculating the network response - the GPC cards also service the rail-mount I/O cards through optical fibre connections.