Option ROM and I/O Space Allocation

Bootable devices such as onboard I/O or PCIe express modules require option ROM and I/O space to boot. However the total option ROM and I/O space for the system is limited by the PC architecture and is allocated automatically when the system is booted. If your system includes many potentially bootable devices, you must decide which ones you wish to boot from, and configure the BIOS to allocate these resources to them.

Option ROM is also required to run some configuration utilities, such as the LSI RAID configuration utility. This utility, which resides in the REM, has option ROM and I/O space allocated to it by default.

Note - These limitations apply to eight—socket systems only. Four—socket systems do not normally encounter option ROM or I/O space limitations.

In systems with the Oracle Solaris OS, an additional limitation might limit your ability to hotplug devices in EM slots 4 and 5.

Option ROM Allocation

The PC architecture provides a total of 128 Kbytes of option ROM space.

I/O Space Allocation

The PC architecture provides a total of 64 Kbytes of I/O space. By default, the BIOS allocates I/O space as shown in the Default I/O Allocation table.

The total available space appears in the Maximum Allocation column.
Some of the space is required for on—board devices. The remaining space appears in the Space Available column.
PCIe express modules and fabric expansion modules require either 4 Kbytes or 8 Kbytes, depending on whether they have a PCIe bridge or not.

Table 4 Default I/O Allocation

CPU Module Slot	Maximum Allocation	Space Available for EMs and FEMs	EM Slots
3	16 k	12k	3.1, 3.0
2	8k	4k	2.1, 2.0
1	16k	12k	1.1, 1.0
0 (master)	24k	8k	0.1, 0.0

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