Intel Extensible Firmware Interface - Manual (Page 850)

Extensible Firmware Interface Specification
19-76 12/01/02 Version 1.10
19.13.7 Bad Break Exception
A bad break exception occurs if the VM encounters a BREAK instruction with a break code of 0, or
any other unrecognized or unsupported break code.
19.13.8 Undefined Exception
An undefined exception can occur for other conditions detected by the VM. The cause of such an
exception is dependent on the VM implementation, but will most likely include internal VM faults.
19.14 Option ROM Formats
The new option ROM capability is designed to be a departure from the legacy method of formatting
an option ROM. PCI local bus add-in cards are the primary targets for this design although support
for future bus types will be added as necessary. EFI EBC drivers can be stored in option ROMs or
on hard drives in an EFI system partition.
The new format defined for the EFI specification is intended to coexist with legacy format PCI
Expansion ROM images. This provides the ability for IHVs to make a single option ROM binary
that contains both legacy and new format images at the same time. This is important for the ability
to have single add-in card SKUs that can work in a variety of systems both with and without native
support for EFI. Support for multiple image types in this way provides a smooth migration path
during the period before widespread adoption of EFI drivers as the primary means of support for
software needed to accomplish add-in card operation in the pre-OS boot timeframe.
19.14.1 EFI Drivers for PCI Add-in Cards
The location mechanism for EFI drivers in PCI option ROM containers is described fully in
Chapter 12 (section 12.4.2). Readers should refer to this section for complete details of the scheme
and associated data structures.
19.14.2 Non-PCI Bus Support
EFI expansion ROMs are not supported on any other bus besides PCI local bus in the current
revision of the EFI specification.
This means that support for EFI drivers in legacy ISA add-in card ROMs is explicitly excluded.
Support for EFI drivers to be located on add-in card type devices for future bus designs other than
PCI local bus will be added to future revisions of the EFI specification. This support will depend
upon the specifications that govern such new bus designs with respect to the mechanisms defined
for support of driver code on devices.