Can someone explain to me what the S76 Core and E24 Core do, how they fit into the boot flow, and where the documentation might be for them? There is very little. The most I could find is “The U74 Cores and E24 core communicate via Mailbox”.
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S7/E24 are both not used at all. E24 might be used as a real-time processor, most relative data are in TRM but not that enough. There’s a currently closed soure binary could control e24 in linux here: soft_3rdpart/e24 at JH7110_VisionFive2_devel · starfive-tech/soft_3rdpart · GitHub
For S7, more information here: Multicore Heterogeneous OS ( Linux, RTOS), is it possible? - HiFive Unmatched - SiFive Forums
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Thank you for the info. The posts are actually really helpful. Hopefully the StarFive team puts out more documentation. That’s really the only thing holding me back for using it.
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Won’t that need the E24 core to be enabled in the .dts(i) file? I see S7 is enabled but why didn’t the E24 core get the same treatment?
StarFive appear to be ignoring the E24 core for SBC (linux) use-cases. Maybe it will be addressed later, but more likely is that any support needs to come via the community.
The JH7110 itself has applications in Auto, Aerospace and other fields, where an independent real-time core could be very handy.
The interesting thing (for me) about the S7 core is that it is pretty equivalent to the 4 main cores, the biggest difference is not having floating-point extensions.
An interesting fact: Floating point operations are not allowed in the Linux Kernel, and are strongly depreciated for modules.
I wish I understood the linux kernel/userland architecture better; since it seeems to me the kernel could run on the S7 with all user processes running on the U74’s.
Which I suspect is a nonsense suggestion due to architecture etc, but the possibility still intreagues me…
S7 doesn’t have MMU, so linux can’t run on it. Though Linux has riscv nommu support, but that needs to recompile the kernel and not safe.
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Thank you, that was the sort of thing I suspected would make this impractical.
The S7 does have one unique ability, It has access to the protected memory and secure data enclave (DTIM). I’m not sure how/if that is being used.
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Some effort has been started to bring Zephyr to the JH7110. It would target the S7 core.
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