PCI: Difference between revisions

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int 0x1a PCI BIOS presence check, fix function selection to use AX instead of BX

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Revision as of 18:13, 17 May 2019 (view source) osdev>Nakst No edit summary ← Older edit		Revision as of 21:34, 4 April 2020 (view source) osdev>Benjaveri m (int 0x1a PCI BIOS presence check, fix function selection to use AX instead of BX) Newer edit →
Line 124: * computer supports both mechanism #1 and the memory mapped access mechanism For BIOS systems, "int 0x1A, BXAX=0xB101 (PCI BIOS presence check)" will tell you if the system uses mechanism #1 or mechanism #2. If this function doesn't exist you can't be sure if the computer supports PCI or not. If it says mechanism #1 is supported you won't know if the memory mapped access mechanism is also supported or not. For UEFI systems, it's extremely safe to assume that mechanism #2 is not supported; and you can test to see if the computer supports PCI or not by checking to see if the "PCI bus support" protocol exists. If PCI is supported, there's no easy way to determine if (e.g.) the computer supports mechanism #1 or not.