Why does the PXIe-8840QC sometimes hang when starting the PharLap real-time system?

Issue Details

When I start the Phar Lap real-time system on my PXIe-8840QC, it sometimes fails to launch and remains in a hung state. Other times, an MDI error occurs. How can I resolve this issue?

Solution

This is because the “Performance Optimized” option is enabled in the BIOS (version 2.1.10f0) under Advanced > System Profile Configuration > System Profile for your PXIe-8840QC, which enables Hyper-Threading and C-STATE. This can potentially trigger errors in the i7-5700EQ CPU controller.
You can resolve this issue by changing the setting to “OS Defined” in the BIOS.

Additional Information

NI strongly recommends disabling Hyper-Threading and C-STATE when using deterministic real-time systems because:

• Hyper-Threading allows multiple threads per core. In other words, the OS will see one physical core with two threads (logical cores), rather than one core with one thread. The RTOS task scheduler will assign tasks to each thread based on priority. If each core has two threads, the task scheduler will assign tasks to both threads, but the underlying hardware has only one core available to process them. This compromises the determinism of the RT system and increases system jitter.
• C-State allows the CPU to enter a low-power state based on load to conserve power, but the issue is that once a core enters a low-power state, it will take some time to wake up and become ready to process tasks. This impact affects system jitter. Worse still, if the system is multi-core and some cores enter a low-power state while others do not, it will result in additional delays for tasks assigned to the low-power cores.