Perhaps a key to the initial success of the Z80 was the built-in DRAM refresh, and other features which allowed systems to be built with fewer support chips (later on, most Z80 systems have been embedded systems, which typically uses static RAM and hence does not need this refresh).ДЇor the original NMOS design, the specified upper clock frequency limit increased successively from the introductory 2.5В MHz, via the well known 4В MHz (Z80A), up to 6 (Z80B) and 8В MHz (Z80H). The Z80 took over from the 8080 and its offspring, the 8085, in the processor market, and became one of the most popular 8-bit CPUs.

Non-multiplexed buses ( the 8080 had state-signals multiplexed onto the data bus).

A built-in DRAM refresh mechanism that would otherwise have to be provided by external circuitry.

Single-phase 5В V clock ( the 8080 needed a two-phase high-amplitude clock generator).

Single 5 volt power supply ( the 8080 needed -5V/+5V/+12V).

Less hardware required for power supply, clock generation and interface to memory and I/O.

Two separate register files, which could be quickly switched, to speed up response to interrupts.

A non maskable interrupt (NMI) which can be used to respond to power down situations and/or other high priority events (and allowing a minimalistic Z80 system to easily implement a two-level interrupt scheme in mode 1).

A more automatic and general vectorized interrupt system, mode 2, as well as a fixed vector interrupt system, mode 1, for simple systems with minimal hardware ( mode 0 being the 8080-compatible mode).

New IX and IY index registers with instructions for direct base+offset addressing.

An enhanced instruction set including bit manipulation, block move, block I/O, and byte search instructions.

The Z80 offered many real improvements over the 8080:

Masatoshi Shima, co-designer of the 4004 and the 8080, also contributed to the development of the Z80. It was designed to be binary compatible with the Intel 8080 so that most 8080 code, notably the CP/M operating system, would run unmodified on it. The Z80 came about when Federico Faggin, after working on the 8080, left Intel at the end of 1974 to found Zilog with Ralph Ungermann, and by July 1976 they had the Z80 on the market. The Z80's original DIL40 chip package pinout In recent decades Zilog has refocused on the ever-growing market for embedded systems (for which the original Z80 and the Z180 were designed) and the most recent Z80-compatible microcontroller family, the fully pipelined 24-bit eZ80 with a linear 16 MB address range, has been successfully introduced alongside the simpler Z180 and Z80 products. Consequently, Zilog has made less than 50% of the Z80s since its conception. This enabled a small company's product to gain acceptance in the world market since second sources from far larger companies such as Toshiba started to manufacture the device.

Zilog licensed the Z80 design to several vendors, though many East European (for instance, Russian) manufacturers made unlicensed copies. The Z80 and its derivatives and clones made up one of the most commonly used CPU families of all time, and, along with the MOS Technology 6502 family, dominated the 8-bit microcomputer market from the late 1970s to the mid-1980s. It was widely used both in desktop and embedded computer designs as well as for military purposes. The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. Total die size is 4950x4720Г‚Вµm utilising a 5Г‚Вµm technology node process. Die of one of the many clones of the Z80A microprocessor.

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