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TheZilog Z80000 is an unreleased32-bitprocessor designed byZilog and completed in 1986. The Z80000 is a 32-bit expansion of the16-bitZilog Z8000 withmultiprocessing capability, a six-stageinstruction pipeline, and a 256-bytecache.[1] It can address 4 gigabytes ofRAM, but cannot execute code written for the Z8000 orZ80.
Described at the time as a "mainframe on a chip", the processor is in many ways an equivalent toIntel's80386. Delays in the initial manufacturing pushed back its availability date to after that of the 386, and the Z80000 only made it to a test sampling phase without ever being released commercially.[2]
Like the Z8000 it is based on, the Z80000 has sixteen general-purposeregisters, but expanded from the Z8000's 16-bit to 32-bit. Like the Z8000, the Z80000 allows its registers to be combined, in this case using two 32-bit registers to act as a single 64-bit one. To support the Z8000s 16-bit wide data, the Z80000 can place two 16-bit values in a single 32-register.
The processor includes amemory management unit that providesprotected memory, important formultitasking, andvirtual memory addressing for temporary storage of RAM on ahard disk. The processor has three methods of accessing memory:
On the Z80000 CPU,interrupts are part of a category known as exceptions. This category includes resets, bus errors, interrupts, and traps.[3]
The processor is designed to interoperate with otherintegrated circuits designed for use with the Z8000, such as theZilog Z8070floating-pointcoprocessor.
The Z320 was theCMOS version of the Z80000.
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