Although fundamentally a 16-bit architecture, some versions had 7-bit segment registers that extended the address space to 8 megabytes.
The register set consisted of 16 16-bit registers, and there were instructions that could use them as 8-bit, 16-bit, 32-bit, and 64-bit registers. The register set was completely orthogonal, with register 15 conventionally designated as stack pointer, and register 14 for stack segment.
There was both a user mode and a supervisor mode.
Like the Zilog Z80, the Z8000 included builtin DRAM refresh circuitry, but although an attractive feature for designers of the time, overall the Z8000 was not especially fast and had some bugs, and in the end it was overshadowed by the x86 family.
The Zilog Z80000 was a 32-bit followon design.