Comparison between Raspian 12 Bookworm on Raspberry Pi 4 and Raspberry Pi 5

Ran the same commands as the OP to test latency, histogram was wierd:
 

Then I realized the "Using POSIX non-realtime" message when starting the latency test despite the PREEMPT_RT kernel. 
 

danielfmo wrote:

Kernel built with latest 6.1.y commit with rt16 patch does boot with previously shared bookwork image.
 

Perhaps change the commit to 6e5a08f736d0366e125a5b84b01d9affc86ddf58
This is when the 6.61 branch was merged into 6.1.y on Nov 3
This will at least lock in a known position rather than just following the head.

For reference we are looking at the 6.1.y commits here  github.com/raspberrypi/linux/commits/rpi-6.1.y  

Raspbian OS uses LXDE as opposed to XFCE so that could be the difference. I can say that I thought latency was better when running with a Raspbian OS on my RP-400. Or there could be other factors at play.

I built a successful non-rt kernel based on 6.1.y and now building a realtime one with 6.1.59 rt patch, patch went with no issues, so that's a good sign.

It's all fun & games so far.

I didn't try the your image rod but notice in the kernel package there was no rp5 dtb file so just assumed it would be a non starter, plus it was 1:00am and the dog was looking at me funny, like it was time for bed.

Update to above, rt kernel built & running. Happy with basic latency test, have sound, BT & wifi disabled. Haven't really pushed it nor isolated any cores. Board is 4GB as new stock of 8GB had no ETA.

Seems like some GladeVCP widgets are not working on Bookworm yet as Wayland is used instead of X11. Gremlin is throwing errors and some others like Actions are not able to initiate.  

Gremlin, none of the HAL Actions and some others are not available in the Glade widgets list.

Has anybody else encountered some issues with the GladeVCP widgets as well?

Piet

The reason all of my images and ISO's run XFCE is that it is an X11 environment. There is a way  to tell Wayland how to deal with X11 via an environment variable but I can't remember how.

I have no idea if this will work or not, but could you please try this Pi5 image I have just built using the same  environment as we used for the official  pi4b image on the Linuxcnc downloads page. It uses XFCE.
drive.google.com/file/d/1H_q0Ra-27ZDOhqu.../view?usp=drive_link

The other problem child I have encounted in the past was VTK was  missing in the Raspberry repos but I see now it is available in Debian. It was a 5 hour compile on a pi4b. (Maybe that was for QTPYVCP who don't offer pi packages in their repo.)