July 1976 with a 2.5 MHz clock rate. The Z80 was a much 8-bit data and 16-bit addressing, and could execute all of the 8080 op codes as well as 80 new ones, instructions that included 1, 4, 8 and 16-bit operations and even block move and two banks of registers (including A and F) that could be interrupt mode. Like many processors (including the 8085), the Z80 featured many undocumented op codes. Chip area near the edge was used for added instructions, but fabrication made the failure of these high. Instructions that often failed were just not documented, increasing chip yield. Later fabrication made these more reliable. The thing that really made the Z80 popular was the memory interface - the CPU generated it's own RAM refreshsignals, which meant easier design and lower system cost. That and its 8080 compatibility and CP/M, the first first choice of many systems. peripherals and an MMU to the Z80. running at 4 MHz for GameBoy software or at 8 MHz for Game Boy Color software. The Z80 was used in the Sega Master System (2003-07-11)
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