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Extensible Firmware Interface Specification
12-96 12/01/02 Version 1.10
12.4.2 PCI Option ROMs
EFI takes advantage of both the PCI Specification and the PE/COFF Specification to store EFI
images in a PCI Option ROM. There are several rules that must be followed when constructing a
PCI Option ROM
• A PCI Option ROM can be no larger than 16 MB.
• A PCI Option ROM may contain one or more images.
• Each image must being on a 512-byte boundary.
• Each image must be an even multiple of 512 bytes in length. This means that images that are
not an even multiple of 512 bytes in length must be padded to the next 512-byte boundary.
• Legacy Option ROM images begin with a Standard PCI Expansion ROM Header
(Table 12-14).
• EFI Option ROM images begin with an EFI PCI Expansion ROM Header (Table 12-17).
• Each image must contain a PCIR data structure in the first 64 KB of the image (Table 12-15).
• The image data for an EFI Option ROM image must begin in the first 64 KB of the image.
• The image data for an EFI Option ROM image must be a PE/COFF image or a compressed
PE/COFF image following the EFI 1.10 Compression Algorithm Specification.
• The PCIR data structure must being in a 4-byte boundary.
• If the PCI Option ROM contains a Legacy Option ROM image, it must be the first image.
• The images are placed in the PCI Option ROM is order from highest to lowest priority. This
priority is used to build the ordered list of Driver Image Handles that are produced by the Bus
Specific Driver Override Protocol for a PCI Controller.
There are several options available when building a PCI option ROM for a PCI adapter. A PCI
Option ROM can choose to support only a legacy PC-AT platform, only an EFI compliant
platform, or both. This flexibility allows a migration path from adapters that support only legacy
PC-AT platforms, to adapters that support both PC-AT platforms and EFI compliant platforms, to
adapters that support only EFI compliant platforms. The following is a list of the image
combinations that may be placed in a PCI option ROM. This is not an exhaustive list. Instead, it
provides what will likely be the most common PCI option ROM layouts. EFI complaint system
firmware must work with all of these PCI option ROM layouts, plus any other layouts that are
possible within the PCI Specification. The format of a Legacy Option ROM image is defined in the
PCI Specification.
• Legacy Option ROM image
• Legacy Option ROM image + IA-32 EFI Driver
• Legacy Option ROM image + Itanium Processor Family EFI Driver
• Legacy Option ROM image + IA-32 EFI Driver + Itanium Processor Family EFI Driver
• Legacy Option ROM image + EBC Driver
• IA-32 EFI Driver
• Itanium Processor Family EFI Driver
• IA-32 EFI Driver + Itanium Processor Family EFI Driver
• EBC Driver