> ‘Open’ means that you’re allowed to understand exactly how it works and that there’s no mysteries. It means having the blueprints of the machine, not a free machine.
No, this is 100% incorrect.
The Power ISA, i.e., the software/hardware interface of the CPU, is open source. This means that if you want to build a Power CPU that implements its software interface, you can do so "for free".
That's it. You don't get "the blueprints of the machine", you cannot look into how the CPU work internally and understand it, etc.
That's like having a standard API that anybody can implement, e.g., the C standard library, but which Apple, Microsoft, etc. ship as a black box binary blob, so you can't understand their implementation, search/fix bugs, etc.
So no, your claim is completely incorrect. The benefits of an open ISA only apply to those wanting to build their own CPUs, which for Power is just not even a handful of companies, none of them making their blueprints of their CPUs openly available...
For end users, your machine is as open/closed on a system with an open ISA like in one with a closed one. People paying 10k$ for a Raptor II in the name of openness are throwing their money away.
This is a completely different situation than, e.g., RISC-V, where not only the ISA is open-source, but the VHDL implementation of many RISC-V cores is also open source, and you can buy those cores today.