More on CUBIX - Was: newbie building a scratch-built computer

Allison ajp166 at
Fri Aug 3 08:43:31 CDT 2007

>Subject: More on CUBIX - Was: newbie building a scratch-built computer
>   From: "Dave Dunfield" <dave06a at>
>   Date: Fri, 03 Aug 2007 07:29:17 -0500
>     To: "General Discussion: On-Topic and Off-Topic Posts"	<cctalk at>
>>> If the whole purpose of this exercise is to have an old 8-bit system so you
>>> can program in hex and/or assembler, then you can download an emulator and
>>> play around with it from there. If you mainly want to run things off the
>>> various serial and parallel ports then something like the Micro-KIM would be
>>> useful.
>There's an experience gained by building it yourself that simply can't be obtained
>by playing with an emulator. Building a real/physical computer is a worthwhile
>excercise and beneficial learning experience. Besides, friends and family are much
>less impressed by a wave of the hand at a PC running an emulator with the statement
>"I downloaded that!" then they are by a rats nest of wires, circuit boards, cables
>and such and "I built it myself!"

There is magic in building it yourself however it's constructed be it emulator
or hardware. The magic is that you have to understand it to build it.  Simply 
assembling "it" does not provide it beyond the mechanical accomplishment
though if you study the result there will be knowledge gained.


>Another plug for my CUBIX system:
>The system comes with the following resident (runs on CUBIX itself) development
>  6809 Assembler
>  ASP - A simple high-level language/preprocessor for the assembler.
>  Debugger (breakpoints, single-step, disassembler, all the usual commands etc.)
>  Basic
>  Forth
>  Micro-APL
>  C compiler
>  8080 simulator
>  Text editors / utilities / etc.
>  - Source is posted for all of the above except for the C compiler.
>I can also provide PC based cross development tools for the 6809 including:
>  Hardware Debug Monitor (RAMless - needs only ROM to run)
>  Full-up ROMable 6809 monitor (Quite powerful)
>  6809 Assembler
>  6809 Disassembler (Does symbols, memory block types, comments etc.)
>  6809 C compiler
>  6809/CUBIX simulator/emulator - Lets you run 6809 code on your PC with ICE
>      type debugging capabilities - Also boots CUBIX, provides access to all
>      the resident tools etc.

He may appear biased but those are powerful tools and unlike back when I 
built my Altair or the 8008 before that they are available!

>I'm obviously biased, but I think it's a worthwhile system to build. Depending
>on your skill/experience/time available, it should take anywhere from a day or
>two to a few weeks to build it. What you get from the excercise is a unique
>system that can actually do useful things, and the experience and satisfaction
>of having created it with your own two hands. Having built it yourself, along
>with the fact that I have released the source code means that you have the
>opportunity to fully understand EVERYTHING about this system - down to the
>tiniest wire, and the last byte of code - this is something that rarely happens
>with modern computers. This system is simple enough that you shouldn't have
>trouble following the design, yet powerful enough to be considered a "real"

MY $0.02, great teaching tool, good for understanding hardware, excellent for
a look at a straightforward OS example that is very usable.  For an old hand
PDP8/11, NS*DOS and CP/M style OSs CUBIX OS was a real eye opener to different
ways files can be orgainized.


>I should also point out that unlike most home-grown designs, the CUBIX system
>is very well documented. Two of the three 360k diskettes that normally accompany
>the system are filled with documentation. Over a dozen documents containing
>more than 300 pages.

Therein lies the greatest value.  Even if you didn't build it there is a wealth
of information that applies to any CPU/system.

>What else can I say - all of the CUBIX material is available free on my site.
>If people are interested, I could organize it into a separate "building a
>CUBIX system" page with more information, additional PC tools and other related
>material. Let me know if there is any interest.

Having built one and meaning to spend more time with it it's a good project
and in some respects less painful than doing a Z80 CP/M machine from the 
ground up.  The key thing is that when operational like CP/M systems there 
is enough software to be useful.  This is unlike the microKIM, CosmacELF 
style minimal systems where hand entered programs of a a few hundred bytes 
are it. 

The other feature is there is a CUBIX SIM and while building you can become 
familiar, read docs, look inside the code and develop software or other 


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