Archived: LabVIEW 8.5 Real-Time Module Known Issues

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This document contains the LabVIEW 8.5 Real-Time Module known issues that were discovered before and since the release of the LabVIEW 8.5 Real-Time Module. Not every issue known to NI will appear on this list; it is intended to only show the severe and more common issues that can be encountered.

Known Issues

All Target Platforms

  • If you format an RT target with an 8.5 format disk or Utility USB drive, you might not be able to downgrade the target to a previous version of the Real-Time Module. To downgrade a target from the LabVIEW 8.5 Real-Time Module to a previous version of the Real-Time Module, reformat the target with a format disk or utility USB drive created for a previous version of the Real-Time Module.
  • When booting an RT Desktop PC target from a USB drive, certain BIOSes hang at the message "Waiting for USB to initialize..." To resolve this issue, remove the USB drive, wait a few seconds, and reinsert the USB drive.
  • If you modify and redeploy a VI, probes can stop receiving updates. After modifying a VI, you should close and recreate probes.
  • If you format an RT target using a utility USB drive, you cannot subsequently format the target using a floppy drive.
  • USB hard drives are not supported on RT targets. If you need to transfer files over USB, use a USB thumb drive.
  • The disk footprint and the memory footprint of the Real-Time Module have increased by over 10% since version 8.2.1.
  • When you create or add a VI under a specific target in the Project Explorer window, not all VIs and functions that appear on the palette are necessarily supported on that target.
  • Indicators that are attached to local variables do not update properly through via remote front panel.
  • Graphs and charts in subVIs do not display properly via remote front panel.
  • The Strings[] property node does not supply a value until you make a remote front panel connection to the application.
  • You cannot run LabVIEW Real-Time targets from secondary or removable hard drives.
  • Queues allocated in RT VIs take up 150% of expected memory.
  • RT targets can hang requiring reboot if you attempt to concurrently add files and transfer directory listings via FTP.


  • On RT PXI 8106 and 8196 targets, performing a TCP/IP write with a string larger than 64kB can consume CPU resources for several minutes.
  • ETS targets can hang if a DHCP server forces an infinite lease time.
  • Some USB thumb drives do not work on ETS targets. The following USB thumb drives are known to work properly on ETS targets: Memorex 1GB USB 2.0 TravelDrive, SanDisk Cruzer 128MB (non-U3), NexDisk USB 32MB (PSD-32N).
  • ETS targets fail to boot if over 2GB of RAM is installed.
  • Desktop PCs that use processors without 64-bit writable RDTSC registers are not compatible with the NI RT Extensions for SMP. You can safely use an affected system as an RT target in single-core mode if you do not install the NI RT Extensions for SMP on the target. To use an RT Desktop PC as a multi-core RT target, the PC must use CPUs with 64-bit writable RDTSC registers.
  • Desktop PCs that use AMD family 0Fh CPUs, distinguished by an integrated memory controller, typically ship with energy-saving features enabled in the BIOS. These energy-saving features can cause instability when the PC is used as an RT Desktop target with the NI RT Extensions for SMP installed. To use an affected PC as an RT Desktop PC target, you must either use the target in single-core mode or disable the energy-saving features in the BIOS. If the BIOS does not allow you to disable the energy saving features, you can safely use an affected system as an RT target in single-core mode by not installing or uninstalling the NI RT Extensions for SMP on the target.
  • The maximum number of files you can open on an ETS RT target simultaneously is 256.
  • If you receive an error while opening a TDMS file, closing the file can crash the RT target.


  • Reading a shared variable that contains no data can cause slowdowns on VxWorks targets.
  • VxWorks targets do not comply with the latest rules for Daylight Savings Time. As a result, VxWorks targets may report incorrect time from early March through early April and from late October through early November. The actual start and end dates of Daylight Savings Time differ from year to year, and not all regions participate in Daylight Savings Time. Refer to the official Daylight Savings Time regulations in your region for more information about the specific start and end dates of Daylight Savings Time each year.

    To prevent time fluctuations on the target, consider disabling Daylight Savings Time in the BIOS. If you need to compensate for Daylight Savings Time on the target, you can use the Set Date and Time VI to update the time at the beginning and end of Daylight Savings Time.
  • The SMTP Email Send Message VI does not work on VxWorks targets.
  • On VxWorks targets, using the Semaphore VIs and the Rendezvous VIs in the same application can cause errors and undefined behavior. You might also encounter errors if the application uses vi.lib\Platform\_goopsup.llb\GOOP Object in addition to the Semaphore VIs or the Rendezvous VIs.
  • RT does not return the IP or MAC address on cRIO 9012 targets.
  • On cRIO 901x targets, DNS lookup has a long timeout on private networks with no DNS server. If the network has no DNS server, there is no need to perform a DNS lookup.
  • Unloading and reloading shared libraries (.OUT files) can cause VxWorks targets to crash. To solve this issue, you can alter the ni-rt.ini file on the target to include the following token in [LVRT] category: InihibitDLLUnload=True. This INI token ensures that shared libraries remain in RAM. However, you must also ensure that the total size of the shared libraries used in the application does not approach or exceed the amount of available RAM on the target.

RT 8.2.1 Known Issues

The following issues from the Real-Time Module 8.2.1 Readme still apply to the Real-Time Module 8.5.

All Target Platforms

  • In Windows Vista, you cannot use the RT Disk Utilities in NI Measurement & Automation Explorer to create bootable floppy disks. However, if you have Administrator status in Vista, you can create a Desktop PC Utility USB drive by selecting Tools»RT Disk Utilities»Create Desktop PC Utility USB Drive in MAX.
  • The Real-Time FIFO VIs have been replaced with the Real-Time FIFO Functions. These functions perform faster and contain additional functionality. For compatibility with upgrading applications, the previous Real-Time FIFO VIs still load from an existing LabVIEW block diagram, but they are no longer available on the Real-Time palette.
  • When you install the Network Variable Engine on an RT target, you also must install the Variable Client Support with the same version number. When you upgrade a target from LabVIEW 8.0.x to LabVIEW 8.2.x, you also must upgrade the Network Variable Engine and the Variable Client Support. For the LabVIEW Real-Time Module 8.2.x, you must install Variable Client Support 1.2 and Network Variable Engine 1.2 on the RT target using the LabVIEW Real-Time Software Wizard in Measurement & Automation Explorer.
  • The Real-Time Module 8.0 returns error code –2222 to indicate that a shared variable with the Enable Real-Time FIFO option selected has no value. The Real-Time Module 8.2.x no longer returns error code –2222 but instead returns error code –1950679034 (0x8BBB0006) to indicate the same problem. This error code is consistent with shared variables that have the Real-Time FIFO disabled.
  • You must enable the W2 hardware jumper to upgrade the RT Engine of an NI PXI-8145RT controller from version 7.1.1 and earlier to version 8.0 or 8.2.x. Refer to the PXI-8140RT Series User Manual for information about the settings and options for the onboard jumpers and switches.
  • In the Real-Time Module 8.0, executables you build with LabVIEW and the Real-Time Module have a .rtexe extension, which is changed from the .exe extension in earlier versions. Although the extension change was cosmetic, in the Real-Time Module 8.2.x you might notice different behavior associated with the extension change. In the Real-Time Module 8.0 and earlier, you can run an executable built with LabVIEW and the Real-Time Module on Windows, and then use FTP to transfer the executable to an RT target and run it when you boot the RT target. In the Real-Time Module 8.2.x, you cannot run an RT executable (.rtexe) on Windows.

    If you want to run an RT executable on Windows and on the RT target, you must create and build two build specifications (one for Windows and one for an RT executable) and drag the necessary VIs for the build specification to each target in the project.

    Executables for VxWorks targets do not run on Windows or on Phar Lap ETS targets.


  • The NI PCI-7041 is no longer supported with the Real-Time Module 8.2.x and later.
  • The following USB thumb drive is not supported for RT target booting or storage: SanDisk Cruzer with U3 smart technology.


  • If you read paths from a file or convert paths from strings and if you use different delimiters for file paths, the paths do not match in comparison operations even though the paths are functionally equivalent but with different delimiters. Review all paths and verify that all use the correct delimiter. Do not use UNC paths.
  • Running the Execution Trace Toolkit on a VI containing Timed Loops might show incorrect thread names of Timed Loop threads if the trace is longer than a few seconds.


Glossary of Terms


  • Bug ID - When an issue is reported to NI, you may be given this ID or find it on  You may also find IDs posted by NI on the discussion forums or in KnowledgeBase articles.
  • Legacy ID – An older issue ID that refers to the same issue.  You may instead find this issue ID in older known issues documents.
  • Description - A few sentences which describe the problem. The brief description given does not necessarily describe the problem in full detail.
  • Workaround - Possible ways to work around the problem.
  • Reported Version - The earliest version in which the issue was reported.
  • Resolved Version - Version in which the issue was resolved or was no longer applicable. "N/A" indicates that the issue has not been resolved.
  • Date Added - The date the issue was added to the document (not the reported date).