Pretty surprising. So IA64 registers were 65 bit, with the extra bit describing whether the register contains garbage or not. If NaT (Not a Thing) is set, the register contents are invalid and that can cause "fun" things to happen...
Not that this matters to anyone anymore. IA64 utterly failed long ago.
There are modern VLIW architectures. I think Groq uses one. The lessons on what works and what doesn't are worth learning from history.
In case someone hasn't heard:
https://en.wikipedia.org/wiki/Itanium
> In 2019, Intel announced that new orders for Itanium would be accepted until January 30, 2020, and shipments would cease by July 29, 2021.[1] This took place on schedule.[9]
It matters to people designing new hardware and maybe new virtual machine instruction sets.