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Z8000 information |
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Zilog Z8000 is a family of 16-bit microprocessors introduced in 1979 between the Intel 8086 and the
Motorola 68000. The series has been designed by Masatoshi Shima and produced by Zilog and second sources AMD,
SGS and Hitachi from 1979 until 1995. Since 1995, the CPU series continues to live and still is in production by Zilog in a pin-compatible CMOS release
called the Z16C00 series (with the Z16C01 as the equivalent of Z8001 and the Z16C02 as the equivalent of Z8002).
There are 4 slightly different Z8000 versions:
- Z8001: large memory version, can address up to 8 MB (divided into 128 segments up to 64 KB each)
- Z8002: small memory version, can address 64 KB
- Z8003: same as the Z8001 with added virtual memory support
- Z8004: same as the Z8002 with added virtual memory support
The Z8000 series introduced a number of attractive new features from the mini-computer and mainframe worlds:
- Regular general-purpose register file (16 16-bit registers that could be used as accumulators, address registers, index registers or stackpointers)
- Separation of Normal and System modes (also known as User and Supervisor modes) for enhancing system integrity
- Large address space (8Mb)
- First commercial Memory management facility (Z8010 Z-MMU)
- Extended Processing Architecture (EPA) allowing co-processing in an efficient parallel fashion
The Z8000 processor also had some drawbacks as compared to its close rival, the Motorola 68000:
- Segmented addressing: maximum segment size of 64Kb which complicates the addressing of very large data structures
- Delayed introduction due to tecnical problems
- Limited support (very limited software base, limited hardware support)
Although initially the Z8000 got some acceptance and was widely recognised to have a very elegant and user-friendly architecture, it became quickly surpassed
by the Motorola 68000 and the Intel 80286 in the commercial domain. In safe-critical environments however the processor apparently continued to play an important role.
References:
Kraneborg Z8000 Homepage
Wikipedia
CPU World
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