- Zilog Z80000
The Z80000 was
Zilog 's32-bit processor from1986 , an expansion of its16-bit predecessor, theZilog Z8000 . It includedmultiprocessing capability, a six-stageinstruction pipeline , and a 256-bytecache . Itsmemory addressing system could access 4gigabyte s ofRAM . Described at the time as a "mainframe on a chip," the processor was in many ways an equivalent toIntel 's80386 . It could execute code written for the Z8000, but was not compatible with the Intelx86 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 providedprotected memory , important for multitasking, andvirtual memory addressing for temporary storage of RAM on ahard 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 accessThe processor was designed to interoperate with other
integrated circuit s designed for use with the Z8000, such as theZilog 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 .
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