Zilog Z80000

The Z80000 was Zilog's 32-bit processor from 1986, an expansion of its 16-bit predecessor, the Zilog Z8000. It included multiprocessing capability, a six-stage instruction pipeline, and a 256-byte cache. Its memory addressing system could access 4 gigabytes of RAM. Described at the time as a "mainframe on a chip," the processor was in many ways an equivalent to Intel's 80386. It could execute code written for the Z8000, but was not compatible with the Intel x86 architecture, nor was it Z80 compatible.

Sixteen general-purpose registers of variable size were available through use of a 64-byte "register file." The processor included a memory management unit that provided protected memory, important for multitasking, and virtual memory addressing for temporary storage of RAM on a hard disk. The processor had three methods of accessing memory:
*compact mode – meant for small programs, could only access 64 kB (equivalent to the Z8000's non-segmented mode)
*segmented mode – 32,768 segments of 64 kB or 128 segments of 16 MB, making a total of 2 GB of accessible memory
*linear mode – direct 4 GB access

The processor was designed to interoperate with other integrated circuits designed for use with the Z8000, such as the Zilog Z8070 floating-point coprocessor.

External links

* [http://www.bitsavers.org/pdf/zilog/Z80000_prelimRefMan_Sep1984.pdf Zilog Z80,000 Preliminary Technical Manual] – PDF scan of documentation from 1984.