I know Allison has mentioned this, but I'd like to provide a bit more detail: In the mid 80's I designed a little 6809 based computer system, including the hardware and all software. The operating system is called CUBIX, and may be of interest to anyone who wants to build up small homebrew computer. Here is some information to consider: - The system is designed to give high functionality with minimal hardware - you can build a completely operational CUBIX system with a fairly small handful of parts. (I have built working CUBIX systems in a single afternoon). - CUBIX is designed to be very portable - it can handle pretty much any I/O devices and disk geometry, and you can even change to new devices or redefine the disk geometry "on the fly". The system is so portable, that many system ports can be done from nothing more than the ROM image (I provide a detailed porting document). - CUBIX itself occupies the better part of an 8K ROM, and provides a nice file system, a command line "shell" (including a good selection of build in commands and "script/batch" files), and over 100 system calls/services. - There are a couple dozen applications and utilities, which include - All the standard file and system maintenance utilities - Several editors, including a fairly decent one which operates line- by line or full-screen visual. (The system includes a TTY specification subsystem which allows you to taylor the screen oriented programs to pretty much any terminal.) - HELP : A vax/vms like help command, which provides interactive documentation to all commands, applications and utlities. - ASM : 6809 assembler, and RAID : a fairly powerful 6809 debugger. - BASIC - FORTH : A very fast FORTH which compiles to directly executable 6809 machine code instead of threaded lists. - MAPL : A little APL system. - SIM80 : An 8080 simulator - allowed me to run most of the code I had written for my Altair on CUBIX (I included on the disk as examples, an 8080 BASIC interpreter, and an 8080 CHESS program) - Lots more... - The system is quite mature/stable - I used it as my main computer for several years, and there has been a small base of other users. (At one time I sold the software as a commercial product). - The system is very well documented. The main documents are: - CUBIX system users guide - CUBIX system programming manual - CUBIX porting guide - Separate documents for all of the major applications. - The distribution "documents" diskette, as a 360k 5.25" disk which contains nothing but documentation, and it is completely full - not a single free sector. - All source code, documentation and bnaries are now freely available. - I have provided schematics for a simple CUBIX system using a serial console, and matching sample drivers. - I have done a PC based simulator for my original D6809 portable computer, which allows you to try the system out by running it (full functionality) on your PC. I also have a command to import/export individual files to/from the simuilator disk images, and you can use my ImageDisk program to transfer disk images back and forth between the simulator image files and physical CUBIX compatible diskettes. - Since I've recently gotten "going" on this system again, I am thinking about writing a CUBIX compatible library for my 6809 C compiler and port it over to CUBIX so that the system will have a resident 'C' development system. If there is interest, I would definately do this. Although it would be considered a "toy system" by modern 32/64 bit standards, a CUBIX system gives you a pretty powerful computer with minimal hardware, and can be a very rewarding small project (as a number of people have told me over the years). It also gives you a very unique system that you won't experience anywhere else. One thing that I have put together for Allison who is building up one of these systems is my "Ultimate 6809 ROM" - I would be happy to make the content available to anyone else who wants to build a system. This is a 27C256 (32K) rom which maps into the 8K CUBIX system address space using two switches to set the 8K bank which will "come up" when the system is reset: Bank 0 contains the CUBIX OS - this would be selected for the normal operatinal mode of the system. Bank 1 contains HDM09 - my Hardware Debug Monitor - this is a very simple monitor which does not require ANY RAM to operate - You can use it to "poke around" the system if only the ROM and console UART are operating (and you can use it's polling accesses to debug the console, so all you really need is the ROM). Since there is lots of extra space in this bank, I have also provided stand-alone/ROM versions of BASIC and FORTH which can be launched from the monitor - these are very handy if you need to write a little program to test your hardware (But they DO require operational RAM :-) Bank 2 contains MON09 - this is my full-featured 6809 debugger, which has full dump/edit memory/registers, disassembly, breakpoints, single-step, NMI "break" of executing programs, and lots of other goodies. It can also download Intel or Motorola format download files so that you can load executable images into the system from a serial device and run them. For the "Ultimate ROM", I have expanded MON09 to include the engine from my SIM80 8080 simulator - this version of the monitor has additional commands to dump/edit the 8080 registers, and to execute/step 8080 code (all the other commands are common) - For those of you who are more familier with 8080/Z80, this lets you test out the system using 8080 binaries - even though it's a 6809 processor! Bank 3 contains a stand-alone/ROM version of the Micro-APL system (I had to put SOMETHING in the last bank!) - Thsi can be handy if you want to write fairly complex test prgorams. I invite/encourage anyone who wants to experiencing building a small/useful computer "from the ground up" to check out the CUBIX system - Most of the material mentioned above can be found on my web site (See URL in sig) - go the the "Dunfield 6809" computer under "Homebuilts". Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.parse.com/~ddunfield/museum/index.html