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Zilog Z80 turns 50 as an open-source replacement heads to drop-in DIP40 silicon — iconic 8-bit CPU launched in July 1976 and was discontinued in 2024
The Zilog Z80 has just turned 50 years old. This iconic 8-bit processor first went on sale in July 1976 and stayed in production for 48 years until Zilog, now a Littelfuse subsidiary, stopped accepting orders in June 2024. However, there’s an open-source replacement closer than ever to shipping in the chip’s original 40-pin DIP package thanks to community-funded fabrication.
The original Z80 packed 8,500 transistors on a 4μm process and typically ran at 2.5 MHz, with later CMOS variants reaching 20 MHz. Binary compatibility with the Intel 8080 let it absorb the existing CP/M software base, with an on-die DRAM refresh counter that cut the number of support chips a system needed. Development of working prototypes cost roughly $400,000 against $500,000 in funding from Exxon, per the Computer History Museum.
The chip powered the ZX Spectrum, TRS-80, MSX machines, Nintendo's Game Boy, Sega's Master System, the Pac-Man arcade cabinet, and Texas Instruments' graphing calculators, then shipped in industrial controllers for decades after home computing moved on to more powerful successors. Zilog's end-of-life notice, dated April 15, 2024, told customers its wafer foundry was discontinuing support for the Z84C00 family, and last-time-buy orders closed that June.
However, Renaldas Zioma's FOSS Z80 project, launched shortly after the end-of-life notice, now has working silicon. The first version, fabbed on SkyWater's 130nm node through Tiny Tapeout 7 on a die of just 0.064mm2, has been confirmed as functional via the project’s GitHub repository. A QFN64 version with all 40 pins exposed followed on the Efabless CI2406 shuttle, two further runs then went through IHP's 130nm process, and the current run targets the classic DIP40 form factor using chip-on-board assembly on GlobalFoundries' 180nm GF180MCU node via Wafer.Space. The end goal here is to fab a drop-in replacement for machines like the ZX Spectrum and RC2014 kits.
The design is built around Guy Hutchison's TV80 Verilog core, and the project's Tiny Tapeout page says the 130nm CMOS implementation should support clocks up to 50 MHz, against 4 MHz for the original NMOS part.
Zilog is trimming the Z80's official successor line as well. A product change notification from last October put the eZ80L92, along with several Z8F-series microcontrollers, on end-of-life, citing "little to no demand." Last-time-buy orders closed on January 20 this year, with shipments scheduled through April 20, on non-cancelable, non-returnable terms. The eZ80L92 is the only eZ80 part named in the notice; the pipelined eZ80 architecture, introduced in 2001 and still inside TI's current TI-84 Plus CE calculators, otherwise remains in Zilog's catalog.
Hobbyists keep finding work for the original chip regardless. For example, earlier this year, a developer ran a tiny conversational AI on a Z80 with 64KB of RAM.
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Luke James is a freelance writer and journalist. Although his background is in legal, he has a personal interest in all things tech, especially hardware and microelectronics, and anything regulatory.
A Z80 can be replaced by a circuit of 60 TTL IC's, without FPGA. This includes a 640x400 VGA, in color. It runs a nice GUI, and you can build it yourself. Search: Isetta computer. AFAIK it is the first time that the Z80 was replicated by a TTL circuit. The Isetta also runs ZX Spectrum games.
The Gameboy doesn't use a Z80 - it uses a Sharp SM83.
The SM83 lies about halfway between the 8080 and Z80 - it is also compatible with the 8080, has some extended opcodes from the Z80 but not all, doesn't have the index or shadow registers, doesn't have the DRAM refresh, etc. It does however have built in timers, and the variant in the GB has built in display and sound capabilities as well.
The good thing was that most Z80's could be overclocked from 2.5 MHz to more than 8MHz providing the memory of the computer was fast enough. try overclocking by the same percentage modern CPU's
I believe the Z80 was pin compatible and instruction set compatible w/Intel's 8088 and could almost be used interchangeably w/the 8088. It broke any programs that relied on timing loops being executed according to the speed of 8088 instructions though and some games would run so much faster on the Z80 as to be unplayable.
All three CPUs were based on the Intel 8080 because the founder of Zilog formerly worked at Intel on the 8080!
Maybe, but 8086 (followed by the 8-bit variant 8088) started the so-called x86 instruction set, which you may have heard about. It is a different instruction set than Z80 and 8080.
Please check before posting disinformation.
Maybe, but 8086 (followed by the 8-bit variant 8088) started the so-called x86 instruction set, which you may have heard about. It is a different instruction set than Z80 and 8080.
Please check before posting disinformation.
The Z80 and 8086 are supersets of the 8080 ISA. Maybe you should check your information.
The Z80 and 8086 are supersets of the 8080 ISA. Maybe you should check your information.
I have programmed both Z80 and 8086 in the 1980s. So I know this since quite a long time. Saying that Z80 instruction set is somehow a "subset" of x86 is just silly nonsense.
