I'll try to explain: Windows (and most OS's that people are familiar with) control which client software has access to resources at a given time, right? So, Windows dictates when any give thread is allowed to run computations on hardware. That means that even though the CPU and video card may be capable of running the computation in extremely short times there is still the question of when those computations are allowed to run. That is: when a thread is serviced. Windows, MacOS, and most desktop variants of Linux do not guarantee that any given thread will be serviced at any given rate. You can try to boost a thread's priority, but that is still not a guarantee. If the computer is in the control loop then I believe that it needs to be able to guarantee a maximum response time for any necessary data, just as the GPS, IMU, sensor fusion, and PID/steering controller must. I do not believe that any typical desktop OS is suitable to be in the loop based on this. A port to Linux is, to me, the first step to moving to a RTOS which would meet the requirement of guaranteeing a maximum time between updating data that the auto-steer system needs.
My concern is not with latency issues per se, and I haven't seen any, but with a lack of certainty. I actually have seen (on a similar but completely unrelated project that I mentored for a while) that Windows will not service a thread for hundreds of msec up to or over a second on a regular basis. It depends on what else is running, how the system is configured, and what the multi-threading code in Windows looks like on that release. I'm not a controls guy, but from I know most industrial systems get around this problem using PLCs or similar embedded systems that run the controls logic and communicate back to data collection/UI programs running on desktops where msec scale timing is not important.
Hopefully that makes my concerns clearer? I do realize that this will seem like minutia to many people, but like I said previously my background is in RF hardware research so it's the way I think. And I think it's valuable and important enough that I am willing to put in effort on this.