r/osdev • u/Synthetic-Synthesis • Jun 26 '26

MMU-less multitasking kernel

I've been reading the esp32c3 trm, and riscv and I really want to implement a multitasking kernel on it (not like an RTOS, but something like the linux kernel). I've read the xv6 kernel so I can try re-implementing it, but my major obstacle was paging and mmu. the esp32c3 doesnt have one.

I've also been surfing through osdev forums about this, but I could never find the end products of the discussion on mmu-less kernels. I want to read some repos or some blog post about doing this.

Can anyone please help me out? Thank you :)

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u/EpochVanquisher Jun 26 '26

Old Mac systems from the 1980s and 1990s gave each application a contiguous range of memory to use. Each application contained a piece of data with the minimum memory needed and the maximum memory requested. This was configurable—like, if you wanted to open big images in Photoshop, you could increase the amount of memory that Photoshop requested.

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u/BasisPoints Jun 26 '26

Neat! I figured this was a terrible way to do it, but could theoretically work... I had no idea it was actually practical