> Difference is Sun was providing a "full stack" proprietary product including CPUs running a proprietary ISA, Unix OS, compiler, desktop environment and productivity apps.

SPARC was not proprietary, buy fully licensable:

* https://sparc.org

Fujitsu sold their own SPARC servers for many years with their own CPUs, and many third-parties put Fujitsu SPARC CPUs into (e.g.) laptops:

* https://jasoneckert.github.io/myblog/sparcbook3000st-the-coo...

Can you get an x86_64 CPU from someone other than Intel or AMD? x86 is much more proprietary than SPARC ever was.

Sun used the non-proprietary Open Firmware (IEEE 1275) for booting (also used by Apple with PowerPC), and SBus (IEEE 1496) for cards before moving to PCI. SCSI and Ethernet/IP were there since forever as well.

The "proprietary" label on Sun, at least when it came to hardware, was always a mystery to me.