You beat me! CHERI totally made me think about those machines.

There's some good background here for those who are interested: https://www.smecc.org/The%20Architecture%20%20of%20the%20Bur...

The architecture of the B5000 / B5500 / B6500 lives on today in the Unisys ClearPath line. I believe the OS, MCP, is one of the longest-maintained software operating systems still in active use, too.