Fuzix OS

For source code and licenses please visit the Github repository. The matching tag is '0.4'.

Install Images

Install images for 0.4 targets. See the git source README files in Kernel/platform-* for install information.

Fuzix 0.4 Release Notes

Overview Of Changes

The core of the Fuzix kernel remains much the same for this release. A number of bugs have been fixed and some interfaces improved. The networking layer has been completely reworked to be more modular so that in future it can run in a different address space to the kenel on 8bit machines.

Executable formats have changed. The 8080, 8085 and Z80 binary formats are now properly unified so that 8085 and Z80 can run 8080 binaries directly. The 68HC11 and 6803 formats are somewhat different but the syscall ABI is arranged so that the 68HC11 can run 6803 binaries.

The 32bit binaries that were using a bodged Linux binflt format are now using a.out with some small extensions to handle the relocation maps. This should hopefully now become a stable executable format for the future.

Building has, where possible, been made easier. The tool chains remain a bit of pain because of the fact many are somewhat obscure, and those that are not tend to get broken on a regular basis forcing specific releases to be used. The actual system build however now has a "make diskimage" target that puts together all the pieces for a bootable system in one go rather than requiring the builder understands the finer details of the system in question and how to merge all the pieces together.

The make environment is much better than it was. It is still terrible however so a "make clean" is needed when switching processors and a "make kclean" is strongly recommended when tweaking any kernel config options or switching target. A lot of the make rules have been merged which should make the problem of sorting out all the rules and dependencies more tractable for 0.5.

Naming Changes

The N8VEM project rebranded as 'Retrobrew' at the request of its founder who had ceased to be so involved. The 0.3 release fixed most N8VEM naming, 0.4 completes this.

There is now a distinction between RC2014 (the product line) and RCbus (the bus standard). In particular the bus has been extended beyond the original concept and now has its own standard document and keepers. Fuzix should now only use the 'RC2014' nomenclature for official RC2014 products but there may be a few that have been missed. Systems that were previously rc2014-xyz are now rcbus-xyz.

Dropped Systems For Now

None of the testers for this work are currently available.

Not Tested (even on emulator)

Supported Processors

6303 / 6803

Hitachi 6303 and Motorola 6803 processors. These are supported by the CC68 compiler chain and tools derived from cc65 and specifically designed for Fuzxi. Currently the only target board is the rcbus 6803/6303 processor card. Floating point is not supported, but adding it would only require someone writes the basic underlying soft fp routines (add, subtract etc).

Other targets should not be hard to add.

6502 / 65C02 / 65C816

These are supported by cc65 (v2.18 or later). Due to compiler limits floating point is not supported. 65C816 is treated as a 65C02 with extras because of the lack of an open 65C816 compiler.

Currently this port targets the RCbus 65C02/65C816 cards and the PZ1. Most of the "classic" 6502 systems have neither the memory or the I/O, and in most cases even when they are upgraded with some of the late era processor upgrades still lack decent I/O.


This port uses gcc 6809 and lwtools. It supports a range of classic and modern systems including Dragon, Tandy COCO, Thomson and RCBus machines. You may need to use an old lwtools (eg 4.13) if using a modern lwtoools and it reports a segmentation fault or similar from lwasm.


The final generation of the 6800 processor line this port uses gcc and has a very different ABI to the 6800/6803. It can run 6800 and 6803 binaries however, but not 6303. At the moment this port targets the Mini11 SBC and the RCbus 68HC11 card.


Motorola 68000 series processors with flat memory space. The port is now a lot more stable and has a sensible binary format. Processors up to 68EC020 are catered for. An additional memory model has been added for systems with low memory and it is now just about possible to run Fuzix on a 128K system without relying on fast disks. GCC and binutils need to be built in a particular way for pre 68020 processors otherwise they will insert unsupported instructions. See the README for 68000.


The 8080 is supported using the Fuziz C compiler. This is a new compiler so there may be a few bugs left to shake out.


This port now uses the full 8085 instruction set (including the stuff Intel decided to not to document). It uses a new compiler built specifically for Fuzix. This port is thus currently a little bit flaky and there are tool and system bugs to nail down. Performance is several times faster than the pure 8080 build as the extra instructions make a huge difference when executing high level languages. Floating point is not yet supported as it needs the base low level FP routines for 8085 writing

The supported target is the rcbus 8085 card with onboard bank MMU.


ARM M0 is supported using gcc and targetting the Raspberry Pi Pico. ARM M4 targets for the DK-TM4C129X and EK-TM4C129X.


This target is specific to the ESP8266 variant of the Tensilica L106.


A complete port for MMUless NS32K processors. This port is new as of 0.4. It targets the in-progress RCbus NS32FX16 processor card design.

Z80 / Z180 / 64180 / Z84C1X

These processors are all supported by the main tree using a fork of SDCC 3.8. The newer SDCC changes a lot of calling conventions so no move to it has been made at this point. That may change in the future.

Supporting code libraries make most flat Z180 systems trivial and provide all the mapping and peripheral support.

Other Processors

These are processors which are in the tree but not yet fully functional. In some cases this is merely used to help catch portability problems in the libraries.


Work in progress to extend CC68 and Fuzix to the original 6800/6808 processor line. Not yet usable


This is currently just the base sketches for a future PC and Rcbus-80C188 port.


An initial experimental port only


Initial support for booting on an ez80 based platform. In this case the Jee Retro development platform. This should form a good basis for enabling any other ez80 platform, but none have been enabled yet.




Tracking the state of the GCC PDP11 compiler and binutils. Not yet at a point the toolchain works well enough.

Rabbit 2000/3000

At this point used as a build check on the user space. Hopefully some Rabbit board enabling will happen during the 0.5 work.

RiscV 32

Tool chain testing and portability work. At the moment this is another compiler chain that we break. In theory Fuzix should be able to run on some of the upcoming and recent RiscV micro-controllers with 128K or so of SRAM.


This target is being used to slowly debug the C compiler. Not a useable port as the compiler is still a fair way from working correctly.


Warrex CPU6. Being used for compiler debug but also on hold until the documentation of the system is in a better state to make progress.


Work in progress. The Z280 is very Z80 like but the different privilege structure and interrupt behaviour meand that for the Fuzix at least this will need its own variant of the low level core code.

Supported Systems

For more details on each system consult the relevant README.md in that Kernel/platform-xxxx directory. There are othee platforms but if not listed here they are likely works in progress or special cases.


John Winan's 2063-Retro system as featured in his "John's Basement" youtube series. A fairly classic Z80 Retro system with somewhat slow bitbang SD card interface.


The 68K nano design from Matt Sarnoff. A minimalist 68000 system with 16bit IDE interface. This makes a very nice and easy to build little Fuzix box.

Ampro Littleboard

The Ampro Littleboard was a classic Z80 CP/M board designed to be the same size as a floppy disk. This port requires the Plus version of the board with SCSI controller.

Amstrad NC100

An pre-laptop portable word processing machine with PCMCIA slot.

Amstrad NC200

The sequel to the NC100 with a floppy drive and much nicer display.


A port that uses a customisation block plus the CP/M 2.2 BIOS. Intended to make it practical to port Fuzix to systems like S.100 machines where the BIOS is basically the architecture and each machine tends to be a bit unique. If you need to port Fuzix to a platform and do not want to deal with the Fuzix and C side of things this may be a good basis. At the moment it is very basic, but easily extensible to cover other gaps in the CP/M BIOS.


Support for the Tandy COCO2 with 64K RAM and CF or SD card adapter. The kernel is partly flashed onto a cartridge bank to make it all fit nicely. Should also work with a Dragon 64.


The Tandy COCO3


Z80 based system with 8" floppy disk interface. The hard disk is not currently supported due to lack of documentation/example code.


An ARM development board.

Dragon 32

There are two ports specifically aimed at the Dragon machines. Each supports one of Tormod Volden's SD and memory extensions - the NX and the later more featured MOOH. This port should, with the right build options, also work on COCO machines with the same interface.


A fairly generic flat memory Z180 retro system.


Sergey Kiselev's EasyZ80. Very similar to the RCbus and RC2014 systems with 512/512K RAM but integrated onto a single board with battery back up and also IM2 interrupt mode support.


Fuzix for the ExpressIf microcontroller. The onboard wireless is not supported because a) it's not documented and b) we stole all the memory it uses and repurposed it. It does however support using a WizNet 5500 for internet connectivity.

Genie EG64/3

Support for the Video Genie (aka Dick Smith System 80, PMC-80 etc) with the Genie EG64/3 CP/M adapter or the equivalent TRS80 Lubomir soft banker.


Robotron KC87, KC85/1 and Z9001. Not the KC85/4. East German systems produced by Robotron-Me├čelektronik.


A simple flat memory 68020 board by Bill Shen


A retro Z8C415 based machine using the single chip integrated Z80 and I/O.


The classic Australian system yet almost unknown elsewhere. There are a long series of these machines with growing power. At least 128K and some kind of decent disk interface is required. Colour is recommended as the Fuzix kernel does not try and deal with video update flicker on the older video.


Low chip count 68HC11 SBC with 512K of RAM driven directly off a 68HC11, and the upper address pins driven by the 68HC11 GPIO lines.


The are two MSX ports. The MSX1 port is a cartridge based port that can run on any 64K mmeory machine with Sunrise style IDE. There is no support for things like the MegaRAM at this point.

The MSX2 port requires V9938 or higher video, MSX2 style memory and at this point a MegaFlashROM with SD card. There is no support for MSX1 systems with the orignal video and MSX2 memory banking although that would be good to add.


Memotech MTX512 with banked memory and suitable disk adapter. An obscure but rather beautiful British machine.


FPGA based retro system.


The N8 is a fusion of Z180 retrocomputer and sort of not quite MSXish things.


Nascom II or III with CP/M PAL, multiple memory banks and CF adapter on the Z80 PIO plus an RTC.


DX Designs P112. An early 'retro' system using a Zilog ESCC.


The classic Amstrad wordprocessor / CP/M machine. Still somewhat of a work in progress. Note that the PCW16 is a completely different architecture and not supported.


Easten block ZX Spectrum clone. This port is targetted at systems with 256/512K of RAM. For the 128K machines just use the 128K Spectrum targets

Pentagon 1024

The 1MB Pentagon with additional mapping capabilities


A breadboard 68000 system using an ACIA and VIA plus bitbang SD card.

RBC Mark 4

The Retrobrew (formerly N8VEM) Mark 4. A Z180 based design for the ECB bus. Note that 0.4 now requires RomWBW firmware.

RBC Mini M68K

John Coffman's mini 68K system.


There are two Fuzix ports aimed at "official" RC2014 targets.

The RC2014 port requires a 512K RAM/ROM card and supports the bigger RC2014 configurations along with a lot of other compatible RCBus hardware.

The RC2014-tiny port is a "because we can" port that puts the core of the Fuzix kernel in the pageable ROM and pages it in and out in order to run Fuzix on the 64K + pageable ROM setup. This works but isn't recommended. Note that you can (and should!) jumper the ROM card for a 28C256 not a 27C256 part if you are doing this, that way you can quickly erase it and update it.

RCBus (Z80 and compatible)

The following RCbus compatible systems have their own ports referenced elsewhere in this document.

The SBC64/MBC64/ZRCC have their own rcbus-sbc64 target. In general the other Z80 boards are compatible and operate with the RC2014 tree. This knows how to handle Z180 processor cards with the banked memory card, and various variant systems and I/O options.

The rcbus-z180 target handles the many near identical flat Z180 designs that use the RCBus with a 512/512K flat 20bit memory space as well as the modification sometimes used to allow for 1MB RAM.

RCBus (Other)

There are specific ports for RCbus systems with the following processors: 6303 (and 6803), 6502, 6809, 8085, 68008, NS32K. The card requirements vary by port. Please consult the port documentation for detail.


A Z180 SBC with uPD7220 GDC video. The video is not supported in Fuzix at this time.


A minimal system Z180 design by Bill Shen

Raspberry Pi Pico

Support for the Pi Pico embedded ARM board

Sam Coupe

A "super ZX Spectrum" machine that proved to be too little, too late to survive the shift away from 8bit home computers.


A banked memory design that draws heavily on Grant Searle's machine.

SBC v2

Retrobrew SBC v2. Z80 base ECB bus card with simple banked memory. This target is documented heavily and is designed to be a reference for anyone trying to understand how to port Fuzix.


Small Computer Central design with CPU, RAM and OM on one card. Also supports the SC114.


Small Computer Central Z180 design. This tree has been kept apart from the unification of various related Z180 RCbus systems because it also supports the ability to boot from SCM firmware. With RomWBW firmware the SC111 can run either.


Small Computer Central Z80 SBC. Has a different more limited memory mapping model to the standard rcbus systems.


Another Eastern block ZX Spectrum clone that differs somewhat from the Pentagon designs.


Fuzix for a slightly modified version of the Grant Searle classic design. The modifications consist of a single wire and resistor mod to use the full 128K of RAM and a tweak to allow an external timer to provide a timer tick.

Sinclair ZX Spectrum

There are multiple ports for the variants of this system. For the clones and not quite compatible systems please see

The following configurations have ports

128K or later with DivIDE/DivMMC
This port uses the DivIDE/DivMMC memory in low space in order to run Fuzix on the Spectrum systems that lack the ability to map RAM low directly. This port also knows about the ZX-Uno extensions and will use them.
128K or later with SpectraNet and a disk controller
Similar to the DivIDE/DivMMC this port uses the SpectraNet memory in the same way, and needs a disk controller such as a ZX-MMC to go with it.
+2A or +3 with ZX-MMC or similar disk controller
Using the additional memory features on the +2A and +3 machines in order to do rather better memory banking.


Bill Shen's glueless Z80 minimal design. Requires either a rev1 board or a small board mod to correct the memory banking error in the original.


TG Consulting Z80 system


High speed FPGA based Z80 (T80) platform. Runs at 128MHz and supports 8MB of RAM.


Timex reworking of the Sinclair ZX Spectrum. Incompatible, buggy and a bit of a flop. It does however have support for RAM/ROM cartridges and has a nice 512 pixel wide video mode.

Tiny68K / T68KRC

A 68000 based system with 16MB of RAM and a CF interface. The T68KRC has less RAM but an RCbus connector. Both are supported.


Thomson TO8. An initial port to the TO8 platform.

Tom's SBC

Z80 retro computer design with banked EPROM and 64K (or 128K with mod) RAM. Fuzix can run from banked EPROM for a ROM based system or from RAM with the 128K modifier.


Tandy model 1 and model 3 systems (and clones) with an Alpha Supermem or Selector are supported along with the Model 4. The 128K model 4 is supported without a memory extender although the Dave Huffman style mod is supported. The XLR8R is not directly supported at this time.


VTech Laser 200 with the SDDrive adapter.


Yet another Z180 system.


An Easten block design and probably candidate for 'worst home computer keyboard ever shipped'. Fuzix supports a suitable configuration which in practice probably means the modern re-creation.


For all practical purposes the Z50Bus systems except the Linc80 are software equivalent to the RCbus ones and use the same kernel. The Linc80 has its own port but that requires building a DIY memory expansion.

Z80 MBC-2

A small Z80 based system with an Arduino I/O subsystem.

Z80 Membership Card

Sunrise EV stackable retrocomputer. Fuzix requires the CPU/RAM/SD card combination.


Z80 emulated CP/M platform. Useful for debugging and development purposes.


Peter Wilson's Z80 Retro design

Zeta V2

Sergey's floppy disks sized Z80 system with banked memory, PPIDE and floppy controller.


Bill Shen's ZRC. A minimal Z80 system using a CPLD. The machine has 2MB of DRAM. Fuzix has no idea at this point how to use it all because it's not clear what you need 2MB for on a small Z80 system with no graphics.