geerlingguy
Xerxes Pi CM5 Blade with M.2 Slot
The Xerxes Pi is a Compute Module blade designed for 1U racks designed by Rapid Analysis.
It was launched on Kickstarter, and is estimated to ship in late 2025. The board includes USB-C power input, a micro USB port, and a 1 Gbps Ethernet jack. Optional PoE support can be added, and there's an M.2 E-key (up to 2260 size) and microSD card slot on the bottom.
It's on the site here: https://pipci.jeffgeerling.com/boards_cm/xerxes-pi.html
I also backed the Kickstarter and ordered a couple of these myself. Based on the images and some brief checks with the width of a CM4, I suspect that once they arrive I should be able to design a LabStack module to hold two of them. If the dimensions work out then that how I intend to mount them.
Hi @geerlingguy thanks a ton for the video of the early production Xerxes Pi I sent over. I’ve set up these pages on our watch list at RapidAnalysis, so we should be able to jump in and reply to questions or comments quickly.
On the power side, we ran some pretty heavy stress tests on the Xerxes Pi with both CM4 and CM5, using M.2 modules like the Hailo and Radxa AICore. What we found is that not only our boards, but even the official Raspberry Pi carrier boards, can brown out when pushed really hard especially if there’s no heat sink. The issue is made trickier by the fact that CM4 and CM5 use slightly different power delivery circuits.
The good news is we’ve been hammering the new prototypes with CM5s, and they’re holding up really well even with demanding M.2 boards and active cooling.
DO you know how many watts the higher end Hailo and AICore M.2 cards use? I know I've seen issues pulling more than 5-6W on M.2 slots on many Pi boards (first or third party), so I try to avoid higher power cards.
But it would be quite nice if Xerxes Pi could use the higher power cards without issue (there are some NVMe SSDs that also brown out on the Pi 5/CM5 in most people's testing).
@geerlingguy I was able to chat with the Radxa engineers directly and they confirmed the power draw on the AICore AX-M1 is ≤ 8W. The Hailo-8 is rated at ~8.5W but I didn't get a confirmation from their engineers on this value.
We are definitely optimising the Xerxes Pi to use higher power cards and ideally want to prevent all brown outs. There is a max_usb_current=1 config but I have not noticed any difference when using this configuration.
A part of the problem is the very different way the CM4 and CM5 handles power input. You can replicate this problem by putting a CM4 on an official CM5 carrier board and vice versa. It just doesn't work properly.
A solution we are currently working on is to tweak some capacitors and use a jumper to physically separate the CM5 and CM4 power circuits. So far, this is the most robust way we can support all compute modules (not just Raspberry Pis) plus all high powered cards on the Xerxes Pi.
max_usb_current should only affect the USB port current (I think limiting it to 600 mA if the PD circuit doesn't detect 5A capability at 5V, if it's set to 0); it doesn't seem to affect anything else, power-wise.