I'm pretty sure I wrote Z280 checking yep, the Zilog Z280 can address 16 MB of memory. It has separated MMU mapping for code and data (64K + 64K mapped anywhere) ideal for operating systems, but if you never enter this mode, then you can access at the same time 64K at the lowest memory address using the normal instructions, 64K using LDUP, and 64K using LDUD. Of course, you can update the MMU registers as required to access other memory spaces, I used the 8K page size. Besides the CPU has a small cache, so it was faster by a magnitude than a Z80.