Zilog Z80, 8-bit CPU becomes open and free

Zilog Z80, 8-bit CPU becomes open and free

Christian Bassow

Launched on the market way back in 1976, Zilog Z80 is an 8-bit microprocessor that has played a significant role in the development of the computer and electronics industry. One of its “founding” characteristics is that the Z80 was designed to be compatible at a code level with theIntel 8080. This means that programs written for the CPU Intel 8080 could and still can run on the Z80 today, without needing any modifications.

Widely used in many personal computers and embedded systems of the 70s and 80s, we recall its adoption in systems such as the historical Sinclair ZX80ZX81 e ZX Spectrum. However, it was adopted in many other fields, thanks also to the fact that it was a rather economical option.

Zilog Z80, CPU a 8 bit: cosa significa

The term CPU a 8 bit refers to the width of the data bus, i.e. the number of bits that the central processing unit can handle at one time. In another article we talked about the race from 8 bit to 64 bit and why there is absolutely no need for a migration to 128 bit.

The Z80 processor is equipped with a instruction set rich and versatile for its time, which made it possible to create a vast range of applications, from the simplest to the most complex.

In the 1970s and 1980s, the resources of memory e di calculation they were limited. An 8-bit CPU was more than sufficient for the needs of many personal computers and embedded systems of that era. The use of a bus width contained data helped to save computational resources, which are much more expensive and limited compared to today.

The Zilog Z80 clone arrives in 2024: a free and open source CPU

Exactly 48 years later, Zilog announced the Z80 CPU retirement. Incredible but true: after so long, the company was founded almost fifty years ago by the Europen Federico Faggin it still ensured the possibility of purchasing the historic CPUs.

Despite the decades behind it, real geological eras in the field of computing, the Z80 processor has maintained considerable popularity and use. The demand and interest in this processor, which have remained significant, have pushed Zilog to guarantee its availability even today.

Now that the Z80 has reached its “end of life”, this GitHub repository announces the availability of a modern clone of the Z80 CPU. The goal is to keep one of the most iconic processors in the entire history of computing alive.

The first iteration of the free and open source Z80 CPU is developed with Tiny Tapeout 07 using a 130 nm construction process and develops on a die which measures 0.064 mm2 of surface. The construction of the first examples is scheduled for June 2024.

The name of the project, baptized FOSS Z80 (Free and Open Source Silicon Z80), highlights the fact that hardware and software are free and open source: they can therefore be used, studied, modified and distributed freely by anyone.

It is also published on GitHub pin diagramas well as for example the list of now expired patents that form the basis for the development of a CPU like the Z80.

Opening image credit: Christian Bassow, CC BY-SA 4.0 DEED license.

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