André's 8-bit Pages  Projects  Code  Resources  Tools  Forum
(by Google)

GeckOS/A65 V2.0

This is a completely new version of my 6502 operating system GeckOS/A65. From version 2.0.0 on it has a lot of new features:

  • multithreading
  • dynamic memory management
  • relocatable fileformat
  • lib6502 standard library
  • internet support
    2013-10-06 Updated GeckOS to 2.0.9
    2010-01-04 Started this page
  • oa-2.0.0.tar.gz Full source archive. To build the binaries you have to have the xa65 package (see below).
  • oa-2.0.0.base.tar.gz Base archive, without the Gecko and CS/A65 architectures and without the copyrighted BASIC interpreter.
  • oa-2.0.0.lib.tar.gz Source for the supplied lib6502 programs.

For some architecture some disk images are provided:

  • c64.d64.gz D64 file for C64 emulators. Start with "x64 -8 c64.d64 -1541".
  • cbm8x96.d64.gz D64 file for the VICE xpet emulator. Start with "xpet -8 cbm8x96.d64 -model 8296"
  • pet32k.d64.gz D64 file for the VICE xpet emulator. Start with "xpet -8 pet32k.d64 -model 8032"

After starting the emulators do a `LOAD"LOADER",8' and then `RUN'. This should do it. On the C64 and the 8x96 PET you have a libshell (lsh) and an old-style shell/monitor coming up on two different virtual consoles. The standard 32k PET only runs a libshell. You can switch between consoles with the TAB (pet32k), the ESC/@ (VICE/real 8x96), or the F1 (C64) key.

Watch a small demo video here

Due to heavy time constraints I am currently not able to do more development. So there is a not-so-well tested version here. Most improvements are in the FSIBM filesystem, that handles PC disks. Now it can also handle SCSI harddisks (scsi driver added) and also handles 16 bit FATs. It uses a PC-type partition table. It is being tested with the CSA architecture, so this has changed a bit more.
Anyway, there is a TODO file that describes what has to be done for 2.1 and a LOG-2.0 file that describes what has already be done.
Download it as

OS/A65 is a full-featured Multitasking/Multithreading operating system for the 6502. It is preemptive and implements some Unix-like features, like signals, semaphores, relocatable fileformat, standard library, internet support via a kind of simplified sockets and last but not least virtual consoles.

It is extremly scalable. Stripped down to the scheduler and interrupt handling the kernel is only slightly above 2k. In normal embedded systems the kernel has around 4k, with only application programs running. Full featured systems have a 4k kernel, and several support tasks provided system services like TCP/SLIP and (different) filesystems.

The kernel is almost completely hardware independent. All the architecture-specific stuff is in a separate subdirectory for each architecture.

The lib6502 as standard library allows easy access to the system services. Parts of this library are already implemented in another 6502 operating system, Lunix by Daniel Dallmann. This way source code compatibility is achieved.

Version 2.0.0 features a "slipd" server process that brings easy internet access to all lib6502 programs, that can now access TCP connections like files. A stable WWW server running on the OS is built into the slipd daemon. Also a remote login can be done. This way the OS can run programs to for example read sensors and write the stuff to files, which are exported by the WWW server.

The relocatable o65 fileformat used by the lib6502 standard library in version 2.0.0 allows more than one instance of a program being run at the same time without interference, even without virtual memory. Also the very same binaries runs on all supported platforms (if they do not use architecture specific stuff, but lib6502 calls only).

Architectures supported are the C64, as well as my CS/A65 MMU selfbuilt computer and my CS/A65 Gecko board. Also supported are the Commodore CBM8096 and CBM8296 computers, as well as any 32k RAM PET (the 3032, 4032 and 8032)

  • CBM PET documentation. Supported are 40 and 80 column models 3032, 4032, 8032, 8096 and 8296.
  • Embedded systems need not all features. Here is some doc to strip the OS down to the basics (with around 2.5k in the end...)

For the development of OS/A65 programs there are two possibilities:

  • lib6502 with the o65 file format. This allows source compatibility (to some degree) with Lunix, as well as that the program runs on all supported platforms. lib6502 programs are simply assembled with my xa65 crossassembler with the including the file "lib6502.i65" and the assembler option "-LLIB6502" set. This tells the compiler to put "LIB6502" into the file as undefined reference that is resolved when loading. The lib6502 jump table is relative to this address.
  • A system application not only uses lib6502 calls (if it uses them) but also kernel calls. The kernel can be at different addresses for different architecture as well. Therefore you have to add "-LOSA2KERNEL" to the assembler line. This address is also resolved when loading. If the file should also be used as a ROM file, then it has to have a ROM boot header, see the kernel description.
  • Here is the cross assembler xa you need to assemble the whole stuff
  • How to build the binaries
  • A description of the files in the archive
  • kernel interface
  • lib6502 description
  • Operation without an MMU
  • introduction to the devices
  • filesystem interface
  • The README that comes with the binary.
  • The README.c64 with instructions how to run it on the C64
  • The README.slip with instructions how to run the TCP/SLIP software
  • There also is a list of Known Bugs
  • There also is a list of Ideas what to do next...
  • An instruction to the lib6502 lsh
  • Overview over the Computer System and its Software
  • The old standard library has been replace with the lib6502 and is not longer supported.
  • The old summary of shell has been replaced by the lib6502 lsh and will no longer be developed.
  • The old monitor is still supported, but not actively developed any more.
  • summary of features and extensions of the BASIC interpreter (c) Commodore
  • The ChangeLog for version 1.3.* and for the development of 2.0.0.

I didn't dream of this becoming such a nice project when I started building this computer in 1989.

After someone asked me to release it to the public, I decided to put it under the GNU public license. (Which, of course, doesn't hold true for the ported BASIC interpreter, which is taken from the C64. See this file for more.) Also the character ROMs are taken from the C64. However, Commodore in its old form doesn't exist anymore and attempts to contact the new right holders have not brought any success, so I put them here.

Well, when I did this project, it was just for fun. But now I find it quite nice. Well, if you know some magazin that would like to publish some of it, I will be glad writing an article or so (if anybody really wants it ;-)
But on the other hand my interests have moved. Occasionally I still work on the project - when I have the time (or take the time ;-)
But after all, I don't really have time for it.

  • vt100 control codes for the console.
  • native C128 port
  • in this process abstract a kind of block device from fsibm and use it for the VC1571 as well

Return to Homepage

Last modified: 2013-10-13

Follow my 8-bit tweets on Twitter (In new window)


Discuss my site on this forum thread

(Forum registration required to post)


Dive into the retro feeling and build yourself a Commodore PET replica

Need more speed? Speed up your 6502 computer with this 10 MHz 6502 CPU accelerator board

Interested in electronics design? Look at the design lesson I got from Bil Herd, the hardware designer of the C128

Want 64bit? - pimp the 6502 with the 65k processor design!