Can't boot into RTAI kernel

I am trying to install LinuxCNC on a PC I've got from my University. I have a bunch of these, and they used to be thin clients, but are now available to re-purpose. They are based on VIA Eden CPU, and they are small, equipped with PSU and LPT port - basically a great thing to run EMC2 on. This is the documentation .
They have no CD drives and can't boot from USB, so I've set up a PXE image of Debian Wheezy, and it boots and installs just fine. The system works flawlessly with X server and LXDE, everything is in order, but it wouldn't boot into RTAI kernel provided by LinuxCNC. I've tried both 686 and 486 versions with no luck. Just after the GRUB it gets to a blank screen, no kernel log is printed, and all i see is "_" in the left corner of the screen. Am I missing something? What could be the problem here?

They didn't, but I plugged CF cards in the IDE. I don't thunk that the issue is with how I install it, it boots into regular Debian just fine, the issue only exists with RTAI kernel. I think it's something about one of the modules bot working with my hardware, but I don't know how to debug it...

Not yet. I wanted to try today, but I grabbed a broken one (with burnt GPU). I would post here as soon as I would get ANY info like tty logs.

Here is a picture by the way.

you could try the 32 bit 4.0 kernel. Have you tried it yet?

sudo add-apt-repository 'deb highlab.com/rtai/2017-01-10/ jessie main'
wget highlab.com/rtai/2017-01-10/dists/archive-signing-key.gpg
sudo apt-key add archive-signing-key.gpg
sudo apt-get update
sudo apt-get install linux-headers-4.1.0-1-rtai-686-pae
sudo apt-get install rtai-modules-4.1.0-1
sudo apt-get install linux-image-4.1.0-1-rtai-686-pae

Oh, thanks, cncnoob1979, I'll try that one too, but I don't think it would work, because it uses PAE.
For now I have some news about it - for anyone who wants closure.

I've had no luck with any kernel/version combination and RTAI patchset, I've tried many kernels, and ANY RTAI kernel just refuses to boot. It doesn't print anything to the serial console or tty0, nothing at all. Just hangs indefinitely, without ever being started. I think it has to do with the patchset itself. So next thing I've tried was Machinekit, and I've installed Jessie for it - what I've noticed is that the machinekit kernel has PAE enabled. I tried booting into it, and something different happened - instead of booting into it the PC just rebooted. I've installed stock PAE kernel, and it also reboots the thing. So I've made my own kernel, disabled PAE and applied the Xenomai patch. It managed to boot in that one! I've used Jessie's linux-patch-xenomai on a vanilla kernel, and it worked like a charm.

I've disabled the PAE support, made it so that the x86 family would be 686 as reported by /proc/cpuid, and now it boots and runs with max jitter of 43000ns on the servo thread. I'll try and tweak it some more, because at first it had crazy jitter (>300000ns), but after I've plugged in PCI GPU it reduced drastically. I think it's not that bad for a thin client with just 533Mhz and passive cooling, but I would try running it without audio support too. If anyone wants my kernel I could publish a .deb after I'll do some more tweaking, but it has almost everything disabled.

Ok, after compiling the RTAI kernel myself, I can say for sure that RTAI HAL patch is the culprit. Even with the kernel that I've compiled by hand it would still hang right after GRUB, and not do anything. Just like the LinuxCNC stock kernels.
It looks like there is no way around it, at least not one I can spot.

Here are the kernels I've compiled, Xenomai ones, and the one with RTAI that doesn't work, just in case someone would stumble upon this thread. Drive

tommylight wrote:

There is a version of Linuxcnc on DebianDog with rtai 3.4.9, you should give that a try as it runs perfectly on slower machines and has a much beter latency. It is very usable on a 500MHz PIII. Can be installed several ways and used directly from USB, also with persistent changes.
Sorry, forgot to mention it earlier.

Sorry to hijack this thread, but I just tried to down load the Debiandog linuxcnc iso(s) linked to on this page murga-linux.com/puppy/viewtopic.php?t=95640&start=120
drive.google.com/open?id=0Byia5Mkbjfied3JpUHB0YWQ1M1E
But I can't figure out how to make them work. I tried booting directly from the iso in a VM and burning it to a CD and trying to boot it, but the computer just says "Fatal: No bootable meduim found! system halted."
What's the trick to make that dog run.

I was curious because I have an older Linuxcnc system that won't run on the newer Debian Weezy (It still works good on Ubuntu 10.04).