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Faggin designed the instruction set to be binary compatible with the 8080 [19] [20] so that most 8080 code, notably the CP/M operating system and Intel's PL/M compiler for 8080 (as well as its generated code), would run unmodified on the new Z80 CPU.
Many instruction set architectures have instructions that, on some implementations of that instruction set architecture, operate on half and/or twice the size of the processor's major internal datapaths. Examples of this are the Z80, MC68000, and the IBM System/360. On these types of implementations, a twice as wide operation typically also ...
The Z80(i) is an improved implementation of the Intel 8080 architecture, with substantial extensions to the register model and instruction set and with added hardware interface features. At introduction, the Z80 was faster, more capable, and much cheaper than the 8080.
The original Z80 uses two cycles to fetch a simple instruction like OR A, plus two cycles for refresh. An additional waitstate is issued on the MSX architecture. A review of the fetch mechanism in a typical MSX environment helps in explaining the R800: Z80, cycle 1: set the higher 8-bits of address; Z80, cycle 2: set the lower 8-bits of address
Later NEC made the NEC V20 (an 8088 clone with Intel 80186 instruction set compatibility) which also supports an 8080 emulation mode. This is also supported by NEC's V30 (a similarly enhanced 8086 clone). Thus, the 8080, via its instruction set architecture (ISA), made a lasting impact on computer history.
When an instruction changes the program counter, it flushes the instructions that the CPU is currently processing. Available at up to 50 MHz (2004), the performance is comparable to a Z80 clocked at 150 MHz if fast memory is used (i.e. no wait states for opcode fetches, for data, or for I/O) or even higher in some applications (a 16-bit ...
The main processor offloaded the disk, tape, and serial I/O operations to a Z80 processor on a second board. [ 29 ] 1981: Zilog Systems Z-Lab 8000 Programmer's Development System, available as a Model 20 system with 256 KB of RAM and single 24 MB hard drive, priced at $27,000, or a Model 30 system with 512 KB of RAM and dual hard drives, priced ...
The HD64180 will not execute the "undocumented" Z80 instructions, particularly the ones that access the index registers IX and IY as 8-bit halves. The Hitachi CPU treats them as illegal instructions and accordingly executes the illegal instruction trap, redirecting the PC register to address zero.