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A Method of Resolving Collision between DMA and PCI Devices with Shared Address/Data Path to Memory Disclosure Number: IPCOM000007630D
Original Publication Date: 2002-Apr-10
Included in the Prior Art Database: 2002-Apr-10

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Thang Q. Nguyen Chau-Shing Hui


For architectures with a single port access to local memory and accesses to local memory is arbitrated by an internal arbiter between internal Direct Memory Access (DMA) and external Peripheral Component Interconnect (PCI) devices, fairness between the devices can be achieved by limiting the DMAs access bandwidth to local memory; thus increasing the chance of successful PCI devices accesses to local memory. However, this is generally done at the expense of DMA performance and overall fairness is not achieved optimally. There should be an algorithm in ensuring that all devices (external PCI and internal DMA devices) get a fair chance to access local memory and ensuring forward progress in the system without sacrificing the DMA or PCI performance. This document presents a method of arbitration that ensures fairness between internal DMA and external PCI devices while maintaining maximum performances among them.