Compute Modules and the next Zynthian

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Yes, I think we need to consider this question for a ‘V6’ version. The question of whether a next Zynthian should use a standard Pi5 board or an as yet unannounced CM5.

No announcement. I heard that we can expect something by the end of 2024. But no news is good news as far as changing the CM interface. And there are quite a few non-RPi implementations, so it might be a de-facto standard even if RPi Foundation drops-changes it (again).

I believe wifi connections will remain iffy (assuming you agree that is the case now due to enclosing wifi antenna in a metal box), and that a Compute Module would allow us to connect to an external antenna (outside and attached to the box).

Friendliness towards Do It Yourself projects

I think we could make a more DIY board with a CM than RPi - we would be implementing the parts of the RPi that we need. And we could use the CM4IO board as an example. Perhaps use some through-hole parts, allow for choice on some chips, provide test points and access, etc.

Ability to change the compute module

This of course is the most important advantage - for Zynia Migrating ZynthianOS to RISC-V, project name Zynia it means we could swap the Pi CM to a RISC-V CM - and there are about a dozen other options available now, but all AFAIK Arm architecture. It would almost certainly make future RPi updates easier. And this is one of our goals on Zynia - to isolate more of the board-CPU characteristics and allow Zynthian to more easily run in different (Arm, RISC-V, PC?, etc) environments.

Multiple decisions

This doesn’t need to be the same decision for all implementations of the Zynthian ‘architecture’ - eg ZV6, Z-mini Zynthian mini , etc.

Although I mostly agree with @jofemodo that we “zapatero a tus zapatos” I can’t resist pointing out that the open space on the PCB where the CM goes could also have pads for a processor and memory etc. This might be be pure fantasy, and the space might not actually be open, but with extra layers??? I’m thinking a JH7110 chip or its descendant.

Yeah, and we still haven’t heard about CM5, but I think if Zynthian is running from an M2 NVME drive it is less important. If necessary it could be supported via the PCIE port.

I hope I’m not “jumping the gun” bringing this up now in the midst of Oram work - I feel it is a mix of inter-related trade-offs and needs to be discussed in advance of the actual CM5 announcement. We could do this now. In the meantime, I’m working on using a current RPi CM4IO board and CM4 for both Zynthian and Zynia.