Cache Base Register
From SnesLab
The Cache Base Register (CBR) exists on the Super FX. It is located at 303fh. It is 12 bits in size. (The remaining low 4 bits of 303eh return zero when read).
It is updated whenever CACHE or LJMP run.
Reference
- subparagraph 2.2.2.4 on page 2-2-4 of Book II of the official Super Nintendo development manual