"a base frequency above 5.7 GHz" and 36MB L2 caches.

Also, I'm curious if there are any other dual/multi-ISA architecture chips that are really different and not just 64 bit extensions or things like THUMB.

I found a 1994 patent[0] from Samsung for a Dual-instruction-set architecture CPU with hidden software emulation mode.

IBM developed the PowerPC 615[1] that had either had an x86 core onboard, or it could translate x86 instruction into PowerPC ones. But it wasn't released.

[0] https://patents.google.com/patent/US5781750A/en

[1] https://en.wikipedia.org/wiki/PowerPC_600#PowerPC_615