There is a frequent issue that occurs when interfacing with PCI Express ("PCIe") devices, i.e., "Error Allocating IO Bar for PCI Device". PCIs are the most frequently used and popular interconnects used in computer systems and electronic devices. A PCIe device may fail to be enumerated properly if this type of error takes place.
This document aims to provide a comprehensive guide and solution on how to troubleshoot "Error Allocating IO Bar for PCI Device" issues.
Overview
The process of troubleshooting "Error Allocating IO Bar for PCI Device" issues begins with understanding the basics of PCIe, followed by understanding why the message appears and the steps and procedures to solve it.
What is PCIe?
PCIe is a high-speed, low-latency interconnect which allows multiple PCIe devices to be connected to a single PCIe host (in this case, the CPU). PCIe provides an efficient way to connect multiple devices such as network cards, sound cards, graphics cards, and storage devices. It uses strategies to minimize data transfer latency, such as credit-based flow control, hot-plugging of PCIe cards, and error recovery strategies.
Why "Error Allocating IO Bar for PCI Device" Appears?
The error in question typically appears when the system is unable to allocate the appropriate IO bar address for the associated PCIe device. This happens due to the following reasons:
- If the PE chipset's BIOS does not have enough "IO ports Bits" to allocate for a particular PCI device.
- If there is a conflicting IO Bar Address.
- The System BIOS is unable to allocate the IO port address for a particular PCI device as there are no IO port bits available to allocate.
- The wrong BIOS version of the system installed.
Troubleshooting Steps
The following steps describe how to troubleshoot the "Error Allocating IO Bar for PCI Device" issue:
- Check which PCIE device is throwing the error by going to the BIOS.You can use a tool such as Speccy that can show all the system BIOS configurations in great detail.
- Disable the "IO Bar Auto Allocation" in the BIOS setup. This will prevent the system from automatic IO bar address allocation for the PCIe devices and will allow you to manually assign an address for the PCI devices.
- Change the BIOS version if possible. After updating the BIOS version, check if the "Error Allocating IO Bar for PCI Device" is still present.
- Verify that the IO BAR address assigned is compatible with the PCIe device's requirement. It is possible that the system BIOS is trying to assign an incompatible IO BAR address.
- Check for any conflicts conflicts between any two IO BAR address assigned in the system. If the system is unable to assign the appropriate IO BAR address due to either hardware or software conflict it will throw this error.
- If all the above steps are not successful, you may need to remove the PCIe device, re-install it, and try the above again.
FAQ
What is PCIe?
PCIe is a high-speed, low-latency interconnect which allows multiple PCIe devices to be connected to a single PCIe host (in this case, CPU). It uses strategies to minimize data transfer latency, such as credit-based flow control, hot-plugging of PCIe cards, and error recovery.
What is the cause of "Error Allocating IO Bar for PCI Device" issue?
The main reason for "Error Allocating IO Bar for PCI Device" is that the system BIOS is unable to allocate the IO Port address for a particular PCI device as there are no IO Port bits available to allocate. It can also happen due to an incompatible IO BAR address or conflicts between any two IO BAR address assigned in the system.
How can I troubleshoot "Error Allocating IO Bar for PCI Device" issue?
The process of troubleshooting this issue begins with understanding the basics of PCIe and then understanding why the message appears. After that, the following steps can be used for troubleshooting “Error Allocating IO Bar for PCI Device”:
- Check which PCIE device is throwing the error by going to the BIOS.
- Disable the "IO Bar Auto Allocation" in the BIOS setup.
- Change the BIOS version if possible.
- Verify that the IO BAR address assigned is compatible with the PCIe device's requirement.
- Check for any conflicts conflicts between any two IO BAR address assigned in the system.
What is the difference between PCI and PCI Express?
The main difference between PCI and PCI Express is that PCI Express offers higher bandwidth and much lower latency than PCI. It also offers better power management and support for small form factor devices. Additionally, PCI Express uses point-to-point transmission instead of shared bus topology.
What is the advantage of using Speccy?
Speccy is a powerful and detailed system information tool for Windows, which is used to monitor system components and software. The advantages of using Speccy are that it provides detailed information about system components such as the processor, motherboard, RAM, GPU, and more. It also allows users to view information in an easy to understand chart and graph format with the option to customise the information view in detail.