Zilog Z8000

(processor)A microprocessor from Zilog introduced notlong after the Intel 8086, but with superior features. Itwas basically a 16-bit processor, but could address up to 23bits in some versions by using segment registers (to supplythe upper 7 bits). There was also an unsegmented version, butboth could be extended further with an additional MMU thatused 64 segment registers.

Internally, the Z8000 had sixteen 16-bit registers, butregister size and use were exceedingly flexible. The Z-8000registers could be used as sixteen 8-bit registers (only thefirst half were used like this), sixteen 16-bit registers,eight 32-bit registers, or four 64-bit registers, and included32-bit multiply and divide. They were all general purposeregisters - the stack pointer was typically register 15,with register 14 holding the stack segment (both accessed asone 32-bit register for painless address calculations).

The Z8000 featured two modes, one for the operating systemand one for user programs. The user mode prevented the userfrom messing about with interrupt handling and otherpotentially dangerous stuff.

Finally, like the Zilog Z80, the Z8000 featured automaticDRAM refresh circuitry. Unfortunately it was somewhat slow,but the features generally made up for that. Initial bugsalso hindered its acceptance (partly because it did not usemicrocode). There was a radiation resistant militaryversion.

There was a later 32-bit, pipelined version, the Zilog Z80000.

单词	zilog z8000
释义	Zilog Z8000 Zilog Z8000 (processor)A microprocessor from Zilog introduced notlong after the Intel 8086, but with superior features. Itwas basically a 16-bit processor, but could address up to 23bits in some versions by using segment registers (to supplythe upper 7 bits). There was also an unsegmented version, butboth could be extended further with an additional MMU thatused 64 segment registers. Internally, the Z8000 had sixteen 16-bit registers, butregister size and use were exceedingly flexible. The Z-8000registers could be used as sixteen 8-bit registers (only thefirst half were used like this), sixteen 16-bit registers,eight 32-bit registers, or four 64-bit registers, and included32-bit multiply and divide. They were all general purposeregisters - the stack pointer was typically register 15,with register 14 holding the stack segment (both accessed asone 32-bit register for painless address calculations). The Z8000 featured two modes, one for the operating systemand one for user programs. The user mode prevented the userfrom messing about with interrupt handling and otherpotentially dangerous stuff. Finally, like the Zilog Z80, the Z8000 featured automaticDRAM refresh circuitry. Unfortunately it was somewhat slow,but the features generally made up for that. Initial bugsalso hindered its acceptance (partly because it did not usemicrocode). There was a radiation resistant militaryversion. There was a later 32-bit, pipelined version, the Zilog Z80000.
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