Specifications

AMD Geode™ GeodeROM Functional Specification 73
7
PCI Support 32087C
7.0PCI Support
This chapter describes the support that GeodeROM provides for PCI device enumeration, configuration, and runtime
access.
PCI bus architecture is outlined in detail by the following documents:
• PCI Local Bus Specification, revision 2.1 or newer
• PCI BIOS Specification, revision 2.1 or newer
• PCI IDE Specification, revision 1.0
• PCI-PCI Bridge Specification, revision 1.1 or newer
Each of these documents is available through the PCI SIG (Special Interest Group) located at http://www.pcisig.com.
GeodeROM supports all PCI 2.1 BIOS functions except those designed to support getting/setting IRQ routing options. This
chapter assumes the reader is familiar with the layout and usage of PCI configuration space. GeodeROM supports the INT
1Ah, B1h PCI BIOS subfunctions listed in Table 7-1.
Directory of 32-Bit Services
GeodeROM provides a 32-bit services table, that is characterized by the ‘_32_’ ASCII signature on a 16-byte boundary in
the address range E0000h-FFFF0h.
The purpose of this table is to inform the operating system of the presence and physical location of the 32-bit PCI BIOS ser-
vices entry point. The layout of this table is described in the PCI BIOS Specification.
PCI IRQ Routing Support
Currently, IRQs are assigned to each device that requires one. All devices are assigned the same IRQ (typically 11) in the
Geode™ South Bridge and their INTLINE registers are programmed to reflect this assignment. Therefore, any operating
systems that execute in conjunction with GeodeROM must provide drivers that are capable of sharing IRQs.
Table 7-1. INT 1Ah, B1h PCI BIOS Subfunctions
Subfunction Number/Name Page Number
Subfunction 01h - PCI BIOS Present 75
Subfunction 02h - Find PCI Device 76
Subfunction 03h - Find PCI Class Code 77
Subfunction 06h - Generate Special Cycle 78
Subfunction 08h - Read Config BYTE 79
Subfunction 09h - Read Config WORD 80
Subfunction 0Ah - Read Config DWORD 80
Subfunction 0Bh - Write Config BYTE 81
Subfunction 0Ch - Write Config WORD 81
Subfunction 0Dh - Write Config DWORD 82
Subfunction 0Eh - Get PCI Interrupt Routing Options 82