Determine Whether You Need to Allocate Option ROM and I/O Space

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If you add a PCIe express module to your server, when the server boots, the BIOS might not be able to allocate option ROM or I/O space to all the devices that require it.

If this happens, when you boot, POST generates error messages. These identify any devices that have not had option ROM or I/O space allocated.

Power on the system to start the BIOS.
During POST, look for one or more messages, such as these.
- For option ROM, the messages look like this:
```
Warning: Out of option ROM space for <device path | address> 
```
- For I/O space, the messages look like this:
```
Warning: Not enough IO address space allocated for device path | address
Warning: Not enough IO address space allocated for device device path | address
Warning: Not enough IO address space allocated for device device path | address
Warning: Not enough IO address space allocated for device device path | address
Warning: Not enough IO address space allocated for device device path | address
Warning: Not enough IO address space allocated for device device path | address
```
Each slot can generate several messages. This is normal.

It is possible that the device you added has been assigned option ROM and/or I/O space at the expense of some other device. If this is the case, the device you added does not appear in the list, but the original device does. This depends on the position of each device in the probe order.
Decide whether you need to configure option ROM or I/O space allocation for one of the following reasons.
- Error messages inform you that a device that you wish boot from has not been allocated option ROM and/or I/O space.
- You wish to be able to run a utility such as a RAID configuration utility on a device that has not been allocated option ROM.
- (Optional) You wish to make the error messages go away.
  
  Note - There is no need to configure option ROM or I/O space allocation simply because of these messages, unless you require the functionality provided by the option ROM and the I/O space.