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Zilog Z80 8-Bit CPU Turns 50, Open-source Replacement Heads To Drop-in DIP40 Silicon (tomshardware.com) 42

Posted by EditorDavid from the once-and-future-chip dept.
An anonymous reader shared this report from Tom's Hardware: 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 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 0.064mm(2), 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...

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..." [T]he pipelined eZ80 architecture, introduced in 2001 and still inside TI's current TI-84 Plus CE calculators, otherwise remains in Zilog's catalog.
In 1999 Slashdot was calling Zilog's updated eZ80 "one of the fastest 8-bit CPUs available today, executing code 4 times faster than a standard Z80 operating at the same clock speed."

Slashdot headline from 2001: Zilog To File For Chapter 11.

Zilog Z80 8-Bit CPU Turns 50, Open-source Replacement Heads To Drop-in DIP40 Silicon More | Reply

Zilog Z80 8-Bit CPU Turns 50, Open-source Replacement Heads To Drop-in DIP40 Silicon

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  • An elegant chip (Score:3, Interesting)

    by memory_register ( 6248354 ) on Sunday July 19, 2026 @08:57PM (#66246984)

    I learned assembly on the Z80, it is super accessible and fun to use. So glad future generations will get to experience the push and pop of a memory stack firsthand.

    • Obsolete. I learned ASM on Itanium and I will proudly pass the tradition down to my prodigy, if I ever find a wife.

    • Re:An elegant chip (Score:4, Interesting)

      by tlhIngan ( 30335 ) <slashdot&worf,net> on Sunday July 19, 2026 @09:47PM (#66247034)

      I learned assembly on the Z80, it is super accessible and fun to use. So glad future generations will get to experience the push and pop of a memory stack firsthand.

      Zilog still makes Z80 based things. They only ended production of the DIP40 package for the Z80. They have various SoCs and microcontrollers using the Z80 processor core. It's a little less convenient if you want to build a Z80 based computer.

      The other alternative is the 6502 which is still available in DIP package as WDC (western design corporation) still makes them. They also have a synthesizable core for FPGAs as well.

      And they are used - the Z80, 6502 and 8051 are still used in many things that need a tiny bit of intelligence (may USB hubs, for example, contain an 8051 core to manage it).

      Though I suspect a lot of that is simply being around for the sake of being around because ARM is slowly taking over the intelligent device market. I don't know why RISC-V isn't appearing more in low end microcontrollers, but ARM certainly is. Which is fine, even though ARM isn't designed to be manually programmed by humans (they designed it more for compilers), it's instruction set is relatively simple and orthogonal so it's relatively easy to learn.

      • Re: (Score:2)

        by AmiMoJo ( 196126 )

        RISC-V is appearing in more and more microcontrollers from Chinese manufacturers, as they seek to move away from dependence on any Western tech. It's still got some way to go to catch up with ARM in performance SoCs, but for low cost microcontrollers it's pretty much on a par now.

        • Re: (Score:2)

          by kiore ( 734594 )
          Yes, for good reasons, China is moving away from dependency on Western tech, but I noticed that they really ramped up the low end RISC-V switch after the June/July 2025 changes to ARM licencing. China already had high performance Xiangshan RISC-V and LoongArch proprietary CPUs.
    • The memory addressing made sense, I liked the register layout, I would highly recommend learning the Z80 or the 68000 if you have never done machine language before. On the old machines, graphics were done by writing to memory addresses, I'm not sure if that is possible to do that anymore in Windows. Machine language was great at that.

      • The Z80 was a pretty easy to learn system. I picked it up as a child wanting to make games on my Amstrad computer, the memory addresing was, imho, easier for a young mind to grasp than the 6510 , though perhaps I'd see that as the other way around had I learned on a 6510 first.

        It is kind of sad in a way to see the Z80s pass into history, but lets face it, you'd feel constrained on a toaster controller with one, in 2026. Though thats probably due to modern coders being a lot less disciplined than the old sch

        • Amstrad... an English Computer I believe, my mother in law had one. I learned Z80 code on a timex/sinclair 1000.
          • I also learned machine code on the Z80 using a TS-1000. The code in the book had an error and I had to learn enough to figure out what they had done wrong and fix it. In the end I got it working. That was a fun little computer.

            • Re: (Score:2)

              by Targon ( 17348 )

              The only negative thing about the Timex was that keyboard. I loved the overall machine for what it was, and it was the first computer I owned. I still feel the Z80 doesn't get enough credit for being one of the dominant CPUs of the mid 1970s to the mid 1980s.

        • I wrote a lot of assembly (back in the day) for both the Z80 and the 6502. The Z80 was like a Mac truck. It had some really powerful instructions (LDIR etc) and a great register-set but the 6502 could be a lot faster on one condition -- that you had space available in page zero to exploit the indirect addressing mode that relied heavily on the first 256 bytes of RAM. The Z80 had the advantage that it had on-chip support for refreshing dynamic RAM so systems with more than 4K or so of memory were much ea

      • Re: (Score:3)

        by AmiMoJo ( 196126 )

        You certainly can write pixels directly into a bitmap on Windows. I suggest using SDL to make your life easier.

        I prefer 6502 myself, but the Z80 has some interesting features. The pseudo-DMA mode, essentially an optimized copy loop, is nice. Quite a few games back in the day used it, notably Ghosts and Goblins on the ZX Spectrum which redraws the entire screen with it every frame. It's a relatively easy to integrate chip, and the port feature allows for a clean memory map and low cost/complexity peripherals

      • Re: (Score:2)

        by Tx ( 96709 )

        On the old machines, graphics were done by writing to memory addresses, I'm not sure if that is possible to do that anymore in Windows. Machine language was great at that.

        That's a system architecture thing rather than a CPU thing. Yes, with the ZX Spectrum for example, there was no graphics accelerator or graphics memory, you just wrote to a particular block of main memory with the CPU, and the video DAC read out that same block of memory to generate the display. You could build a system like that with a mo

    • I hear you. Z80 was my first CPU too. I started with a borrowed ZX Spectrum as a kid (family couldn't afford to buy one, but a neighbor had one, and my father could borrow one from work over the weekends from time to time). I quickly got bored of playing games (loaded from a Grundig cassette tape player - that one we owned), learned BASIC (built-in), then assembly, spent some time hacking games (think unlimited lives, or invulnerability hacks, some of mine were even published in a national computing magazin

    • Re: (Score:2)

      by sjames ( 1099 )

      Z80 was also my first assembly language. Perhaps not super important for me, but it's nice to know the Z80 will continue to exist in some recognizable form.

      IIRC, LANtastic cards (another relic of the past) had a Z-80 on them. It was socketed, no less.

  • After coming from the Intel 8085 in the late 70's.

    Don't you just love copyrighted nmemonics?

    I had a CP/M system which had a Z-80 before I got my first IBM PC clone. It had a 5 megabyte hard drive which I wrote a CP/M BIOS extension for.

    Also used (Sega?) arcade boards I got at the local surplus store which had Z-80's on them for various embedded projects.

  • That's the ticket to truly getting a hang of create more efficient assembler code. Compiled by hand with paper and pencil of course.

  • Meh (Score:3)

    by Aighearach ( 97333 ) on Sunday July 19, 2026 @10:08PM (#66247060)

    This is all somewhat misleading because Zilog still makes 8 bit "eZ80" microcontrollers with Z80 compatibility mode. Though for new designs you should usually use their new 24-bit addressing mode for high speed general I/O and debugging. High pin count versions in stock at Mouser with no EOL warnings listed.

    If you really want to experience the differences between that and a modern instruction set the simulation software should "all" cover it. Probably better off learning RISC5 if you want to get good at low-feature ASM in a more useful context.

  • "So, we tried the biggest node we could find but the die came out too small, we had to find a bigger process node to make it big enough we could handle it to fit it in the package and attach it."

  • Any money programming for Z-80 based systems?

    • Unlikely many companies would be using the Z-80 in any new or current products.

      • Re: (Score:2)

        by 0123456 ( 636235 )

        Last I looked adding a Z80 to your custom chip design was pretty much free so it's highly likely that low-end embedded systems will be using them for many years to come. Of course they may farm out the programming work to LLMs since it's a simple processor which can't run a lot of lines of code.

    • People still develop new games for the Master System (which uses a Z80), the Genesis (which uses a Z80 as a sound coprocessor), and especially the Game Boy (whose Sharp SM83 CPU isn't exactly a Z80 but is similar). And they're selling these games both as ROM filess on itch.io and as cartridges.

  • My first job when getting into computers was on a S100 bus system with a Z80 running at 2 Mhz. It actually was fast for the time because the whole system was written in assembly language. Really had to understand computer from the chip level up back then.

  • I thought it was still popular in embedded systems that don't need 16 and 32 bit architectures? Don't some MCU's run Z80 instructions? I guess the chip is different as it probably includes RAM and other goodies because that's cheaper than using separate chips.

    What kind of CPU's and chipsets does one find in small and cheap gizmos?

    • PIC is often the cheapest at volume so gets used a lot. These days you can get a 32 bit ARM on a tiny 6 pin package, so that often gets used instead even for things that would work fine on 8 bit.

      Personally I prefer AVR over PIC for 8 bit, because it has a GCC port and fits better into the same toolchains as ARM.

      Z80 still exists but it isn't used in very many places. Definitely not popular.

  • With the current price of complex chips, especially memory, the Z80 computing might make a resurgence. Now, if I only could find my trusty CP/M manuals...

  • My first computer was a 1979 Sharp MZ-80K [homecomputermuseum.nl], I spent my school vacations writing Z80 mnemonics code in the day time and hand assembling it to hex code at night. I still have, program and use two MZ-80K machines here in the room with me.

    The Z80 today:

    - Z80 assembler, linker, C compiler and libraries: Z88DK [github.com] was originally developed for the Cambridge Z88 notebook computer but now supports over 100 Z80/8080 machines [github.com].
    - RC2014 [rc2014.co.uk] is an open source modular Z80 computer kit, it runs CP/M and Microsoft MBASIC.
    - Two recent open source designs by The Byte Attic (Bernardo Kastrup):
    - * The Cerberus 2100 [github.com] has a Z80, 65C02 and a AVR processor for I/O. You can build it yourself or buy it from Olimex [olimex.com]
    - * The Agon Origins [github.com] and Agon Light [github.com] have an eZ80 CPU, it runs BBC BASIC. You can build it yourself or buy it from Olimex [olimex.com]
    - T80 FPGA core [github.com] for the MiST and MiSTer FPGA [github.com].
    - The MiSTer implements [github.com] many Z80 systems, including the Sharp MZ series, Sinclair ZX series, Tandy TRS-80 series, MSX, Amstrad/Schneider CPC and PCW series, Commodore 128 (which also has a Z80 CPU next to the MOS 8502 CPU), Jupiter ACE, SAM Coupé, Tatung Einstein TC-01, etc., as well as several consoles and arcade machines.
    - The ZX Spectrum Next and the N-GO [wikipedia.org] implement the Z80 in FPGA, it can also run on the MiSTer.
    - The MSXVR [msxvr.com] is based on the Raspberry Pi.

  • I don't mean that in a demeaning way. Z80 assembly language was my first professional programming job and I spent some years being the department SME. I'm very interested in this, but I don't currently have a use case. In the present time, where we have 64 bit Raspberry Pis, I'm sad to say that I'm not sure there is one.

    I'd love to be wrong about this.

  • Can a Z80 clocked at 5 GHz play Crysis?

  • As one might guess, someone's already done a cycle-accurate pin compatible drop-in replacement for the Z80 using a RPi Pico, and (of course) added a ton of bells and whistles...(SD card, wifi, etc etc)
    https://eaw.app/picoz80/

  • But will an AM radio sound the same? (Score:3)

    by RogueWarrior65 ( 678876 ) on Monday July 20, 2026 @05:49PM (#66248546)

    We used to stick AM radios next to those early computers to give the illusion of sound for games.

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