LinuxCNC on Raspberry Pi 5

Here we go again and now it might have the power to actually work? Key features include:

• 2.4GHz quad-core 64-bit Arm Cortex-A76 CPU
• VideoCore VII GPU, supporting OpenGL ES 3.1, Vulkan 1.2
• Dual 4Kp60 HDMI® display output
• 4Kp60 HEVC decoder
• Dual-band 802.11ac Wi-Fi®
• Bluetooth 5.0 / Bluetooth Low Energy (BLE)
• High-speed microSD card interface with SDR104 mode support
• 2 × USB 3.0 ports, supporting simultaneous 5Gbps operation
• 2 × USB 2.0 ports
• Gigabit Ethernet, with PoE+ support (requires separate PoE+ HAT, coming soon)
• 2 × 4-lane MIPI camera/display transceivers
• PCIe 2.0 x1 interface for fast peripherals
• Raspberry Pi standard 40-pin GPIO header
• Real-time clock
• Power button

Looks good, wonder if it'll support NVMe boot .

why not , you can allready boot RPI4 (CM4) from NVMe

It should work. The benefit here would be the PCI slot.. If someone were to make hardware for it. GPIO step generation is still probably jittery

Just for completeness it's a PCIe x1 slot, not PCI.

Mesa SPI & Ethernet work fine, a 6i24 or 6i25 might work .

Should I get 4gb or 8gb RAM ?
For linuxcnc.

It looks like Raspberry Pi OS gives you the choice of 64 versus 32 bit. 8G makes no sense with the 32 bit OS. Because various objects are larger in 64 bit mode, the 64 bit OS is likely a bit slower. Don't know if the real time extensions work on the 64 bit OS.

In my experience, LinuxCNC is not memory intensive. The biggest memory resource consumer is the X windowing system.

IMHO, 4G should be fine.

In my experience, LinuxCNC/RPi4 occasionally generates some unhappy real time messages  .   Don't think I've ever seen it cause a real problem though.   Haven't updated my OS is a couple years, perhaps the new versions eliminate these messages.

Original plan was to update to RPi5.   We of course know what happened to the RPi5 schedule  .  Looks like RPI5 will soon be widely available  .   

If this is accurate:  gadgetversus.com/processor/broadcom-bcm2...vs-broadcom-bcm2711/    RPi5 has a substantially improved processor.   2-3x performance reports.   But for real time considerations, probably what happens is some task in the OS occasionally goes off and flushes the real time stuff out of the cache.   BCM2712 has double the cache capacity and a claimed 3x memory max bandwidth.   This should significantly help real time performance.

Would expect the real time performance of RPi5 to be quite a bit better.   I think we'll soon find out.

 

Realtime is fine with 64 bit, Rodw and myself have been working on and released images for the RPi 4.
In Australia the 8gb model is only $30 more than the 4gb model, so it's kind of a no-brainer which one to go for. Add the extra 600Mhz per core, the RPi 400 have 1.8Ghz cores, and the faster SD card access life should be good.

I think there was a time when the 8 gb didn't work but getting a 64 bit kernel operational has solved that.
However, on the flip side, Memory usage by linuxcnc is well under 4 Gb.
I think when the Pi5 surfaces, the builder Cornholio and I have built should transfer to it OK as we are using the genuine Raspberry kernel code. One would expect that it will support the Pi 5, hopefully by changing one variable being the board we are building for.
The good news is that our builder has been forked by Linucnc and will become the official Pi image builder when 2.9 is released shortly.
github.com/LinuxCNC/rpi-img-builder-lcnc