The 3DO OS Source Code(archive.org)
archive.org
The 3DO OS Source Code
https://archive.org/details/opera_202201
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For those interested in learning more about the Portfolio OS (besides looking at the code) check out https://3dodev.com and/or come to the Discord https://discord.gg/kvM9cQG. We have a number of homebrew devs including previous 3DO game developers.