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What can causes a jitter at real-time tasks?

As long as no other real-time software or similar system-critical software is installed, (almost) nothing exists, which interrupts or delays the real-time task except:

  • CLI = general interrupt blocked through Windows and drivers. Unfortunately, no software can do something against it; However, in Windows the blocking time is limited and almost the driver is responsible for this; in this case the respective driver has to be replaced; it is difficult to determine it, thus only possible by our support (in return of payment.
  • WBINVD command to flush the entire internal cache. According to experience, only by using Nvidia graphic drivers; only by replacement of the card with an ATI (AMD) the problem can be solved.
  • C1E = Enhanced Power Save Mode of the CPU. Especially, the overdeveloped Intel CPUSs (i7, Xeon, …) turns into the idle mode after short breaks, so that the wake up after a timer interrupt can take several milliseconds. That can be switched of in the BIOS (see CIE or similar) or the PC is not real-time capable.
  • Ordinary Windows activities cannot replace real-time task. Windows has the priority 1, whereas the RealTime tasks have the priorities from 1 to 255. DPC has no influence.
  • To achieve the goal to improve the real-time behavior, only the Dedicated Mode, which supports the exclusive use of single CPU cores in real-time. Without Windows influence the maximum jitter is less than 1 us.