![]() PCI bus protocol is a legacy bus protocol by today’s standard. This article focuses on systems based on the PCI bus protocol. Therefore, you must understand the address mapping mechanism of the specific bus protocol to understand the system address map initialization. Bus protocol being utilized in a system dictates the address mapping of the memory of a device-that’s attached to the bus-to the system address map. ![]() X86/圆4 system address map is complex due to backward compatibility that must be maintained in the bus protocol in x86/圆4 architecture. PCI device memory address mapping is only required if the PCI device contains memory, such as a video card, network card with onboard buffer, or network card that supports PCI expansion ROM, etc. This article explains the initialization of the system address map, focusing on the initialization of the PCI chip registers that control PCI device memory address mapping to the system address map. ![]() Low-level programmers are sometimes puzzled about the mapping of device memory, such as PCI device memory, to the system address map. This article serves as a clarification about the PCI expansion ROM address mapping, which was not sufficiently covered in my “Malicious PCI Expansion ROM” article published by Infosec Institute last year ( /pci-expansion-rom/).
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