Isn't your pursuit somewhat of a wild goose chase? You're only running a servo thread so I'm assuming you have a hardware motion controller like a mesa card, and if that's the case, is there any benefit to having 20us max jitter vs 60 or even 80? I'm sure someone more knowledgeable will correct me if I'm wrong, but with a mesa board even 100us max jitter should be fine. In the context of linuxcnc (and real-time in general), it's more of a "works/doesn't work" rather than "this works faster".
I'm actually quite please with this computer. There are multiple threads here struggling with just the right raspberry pi config with a custom linuxcnc image, or threads about other SBCs working with linuxcnc at all - orange pi, banana pi, odroid and so on, while this one seems to work just fine out of the box with the regular x86 image. No messing about.
I'll do as tommylight suggested and run it overnight soon so we'll see, but that puts us back to the works/doesn't work thing. if it works fine with high jitter, it really doesn't matter that other cpus can do the same job with lower jitter, no?
