In their quest to come up with ever more efficient architectures, concept engineers sometimes do crazy things. Twin registers (also called multiview registers) are one of them: when accessing an address location, it sometimes behaves like it's one register, while at other times it's like there's another register residing there.
This is a companion discussion topic for the original entry at https://verificationgentleman.netlify.app/2015/01/30/vrad-twin-registers.html