Using Bios For Resource Allocation; Legacy Option Rom Allocation - Oracle Exadata X5-2 Service Manual

Using BIOS for Resource Allocation

Using BIOS for Resource Allocation
This section explains how the BIOS allocates Option ROM and I/O resources.
"Legacy Option ROM Allocation" on page 186
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Legacy Option ROM Allocation

In Legacy BIOS Boot Mode, there are PC architecture constraints on Legacy Option ROM
allocation. These constraints do not apply to UEFI Option ROMs, which are often referred to as
UEFI drivers.
Choose Legacy BIOS Boot Mode to allow host bus adapters (HBAs) to use Option ROMs.
Choose UEFI BIOS Boot Mode to use UEFI drivers.
The system BIOS allocates 128 KB of address space for Legacy Option ROMs. This address
space is shared between on-board devices and PCIe add-in cards. This fixed address space
limitation is imposed by the PC architecture and not by the BIOS itself. It is possible to exhaust
the available address space when installing PCIe add-in cards. When the address space is
exhausted, Oracle ILOM displays an Option ROM Space Exhausted message, which means
that one or more devices cannot load Option ROMs.
For example, if you install a SAS PCIe card, you might encounter a message similar to the
following message in the Oracle ILOM event log:
Option ROM Space Exhausted - Device XXX Disabled
By default, all on-board Legacy Options ROMs are enabled in the BIOS. However, you can
disable most of these Option ROMs, unless they are required to support booting from the
associated device or to provide some other boot-time function. For example, it is not necessary
to load the Option ROM for the on-board network ports unless you want to boot from one or
more network ports (even then, you can disable the Options ROMs for the remaining ports).
To minimize server boot time and reduce the likelihood of exhausting the available Option
ROM address space, disable the Option ROMs for all devices that you do not intend to boot
from. Enable Option ROMs only for those devices from which you intend to boot. If Option
ROMs are enabled for more than one boot device, you might encounter an Option ROM space
exhausted condition. If you encounter the Option ROM space exhausted condition even after
disabling all devices from which you do not intend to boot, then disable additional Option
ROMs. Under some circumstances it might be necessary to disable Option ROMs for all
devices except for the primary boot device.
186 Oracle Exadata Storage Server X5-2 High Capacity Service Manual • January 2018