Determining the Number and Range of PCI/PCIe Root Bus Devices

Updated Feb 25, 2019

Reported In


  • PXI Chassis
  • PXIe-8381
  • PCIe-8381
  • PXIe-8384


  • MXI-Express BIOS Compatibility
  • PXI Platform Services

Issue Details

  • I have a PCI/PCIe system and I want to know the restrictions that can't be fixed using the NI MXI-Express BIOS Compatibility Software.
  • I want to know the number and range of my PCI/PCIe Root Bus Devices.
  • How can I determine if my computer's PCI/PCI Express bus has limitations that cannot be corrected by the NI MXI-Express BIOS Compatibility Software?


Usage : 

  1. Download the appropriate version of the application (attached at the bottom of this article) and run it (Only use MXIeBusDetect_32bit.exe on 32-bit Windows systems, and only use MXIeBusDetect_64bit.exe on 64-bit Windows systems).
  2. Look for root bus devices with a status device is running. A full (non-limited) range of bus numbers would be [0, ff]. If this is not [0, ff], this indicates the end-user's motherboard has a limited number of buses to work with, and therefore may not be MXI-compatible.
  3. Press Enter to terminate the program.


Sometimes phantom devices will be seen, as shown below. These can be ignored :


An example of a system with a limited range may have an output that looks like the following :


To save this information to a file, run the executable from the command prompt, piping the information to a text file. For example, type : MXIeBusDetect_32bit.exe > out.txt


Press Enter to execute the command, then press Enter again to terminate the program. The information will be saved as out.txt or as the end-user's desired output filename.

Additional Information

MXI-Express BIOS Compatibility Software works around common BIOS limitations; however, not all possible limitations can be managed. Among the configurations that MXI-Express BIOS Compatibility Software cannot compensate for, some can be detected in advance (prior to installation of software), including:

  • The presence of multiple PCI/PCI Express root bus devices, which adds complexity to the system.
  • A low maximum limit on the bus number range set by the BIOS, which limits the amount of hardware that can be attached to the system.


The installer for MXI-Express BIOS Compatibility Software checks for these issues and alerts detection through pop-up messages. In the case of multiple root bus devices, installation is prevented.

MXI-Express BIOS Compatibility Software versions 1.4 and newer do support multi-root bus systems, though the MXIeBusDetect utility may suggest otherwise when run on certain systems. An alternative to detect these issues in advance is to use a stand-alone application, the MXI Express Compatibility Root Bus Detection Utility, which is attached to this article. It will provide information about the system's PCI/PCI Express root bus devices and the implications of any detected issues. You should only use the version of the MXIeBusDetect exe that corresponds to your version of Windows. 32-bit versions of Windows should use the MXIeBusDetect_32bit.exe utility, and 64-bit versions of Windows should use the MXIeBusDetect_64bit.exe utility.


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