In multi-vendor integrated systems, what type of system level problems can most affect gigabit performance and how can these be resolved?
Most serious system level problems are ones that affects PCI burst-mode bus-master DMA initiated by the gige controller. They usually occur in centrally arbitrated resources like the system controller and SDRAM interfaces. A system controller/SDRAM interface that is not configured for PCI burst transfers, not configured for pre-fetching, incurs excessive retries or wait states or otherwise prematurely terminates or truncates a burst mode bus-master DMA from a high-speed controller like gige can severely limit Gigabit Ethernet performance. It can easily cut performance in 1/2 and in some cases reduce it to 20 percent of its capacity. It is in these cases when the Gigabit Ethernet controller requesting bus master DMA, it is dependent on performance of the host board, system controller and SDRAM interface. The system board vendor should be asked to verify gigabit operation of pci-based burst-mode bus-master DMA and provide performance statistics. In many cases a PCI bus-analyzer is needed
