Using Bios For Resource Allocation; Legacy Option Rom Allocation - Sun Oracle Sun Server X4-2 Service Manual

Using BIOS for Resource Allocation

This section explains how the BIOS allocates Option ROM and I/O resources.
"Legacy Option ROM Allocation" on page 170
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"I/O Resource Allocation" on page 171
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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 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.
170 Sun Server X4-2 Service Manual • May 2014