Run "uname -m" to confirm. If it says aarch64 then it is 64 bit. If it says armv7l then it is 32 bit.
If you want 64b I'd start with
Bootable 64-bit Gentoo image for the Raspberry Pi 4 Model B, and Pi 3 B and B+, with Linux 5.4, OpenRC, Xfce4, VC4/V3D, camera & h/w codec support, profile 17.0, weekly-autobuild binhost
Turned off GPU accel and video4linux and with a 100,000nS servo thread latency is <25,000nS after several hours, but without playing a video.
Kernel 4.19.71, the one that comes with the Rpi4 2.8 img on the LCNC website.
Video is limited to 1920x1080. Overclocked to 2.1Ghz, isolcpus=1,2,3, idle=poll
With video playback latency jumps to 102,000nS after a few seconds. Video is choppy.
A USB GPU might work well enough with the Rpi4. Will try that soon.
We had Xenomai on the allwinners 6 years ago (cubieboards) at 40,000 worst case while playing videos.
For x86 we have
Stepconf is a program that generates configuration files for LinuxCNC for a specific class of CNC machine: those that are controlled via a standard parallel port, and controlled by signals of type step & direction.
Stepconf is installed when you install LinuxCNC and is in the CNC menu.
A similar app could be written for the Rpi to configure GPIO's and test them.
I'm on it, I'll report back. The problem is that all of these files have the same name. Who knows what's what?
By the way, it looks like LinuxCNC launched and actually ran with the other .img, but clearly something is wrong. I wonder if anyone is having luck running a 64bit version of linux on a pi4 and linuxcnc?
Cheers fingers crossed.