CUBIX/6809 updates

[Holger Veit]

woodelf wrote:

> Dave Dunfield wrote:
>
>> (The debug enhancements are brought to you courtesy of the stack
>> corruption bug :-).
>>  
>>
> and the number 6809 ...
> Looking at his home page you got alot more stuff about old machines 
> including a few 8's 11's and 12's.
> I think cubix was a good idea, but this 15 years too late for me as I 
> realize in hindsight that 128k of
> memory - split code and data is needed for any real work. This the 
> crummy 8088 has but not the 6809.

Consider memory mapping, e.g. with the already somewhere mentioned 
74ls610/611/612/613. At least the 612 is still
available from unicornelectronics. Using memory pages is not worse than 
x86 segments. With some external
memory (74F189) it should also fit into a 9572.

> Part of the reason I building a 9/18 bit cpu ( If I can ever keep the 
> same instruction set or bit with --
> next week it could be 12/24 bits using 2901 bit slices rather than the 
> CPLD's I have ) is that I have
> 256k of memory something that I feel is right for a 'small'  
> computer.  With the CPLD's I can run @

What is *right* or *wrong* with a small computer? I think we are 
meanwhile somewhat "damaged" from the
wealth of CPU and memory resources from even mediocre PCs. Small systems 
are attractive IMHO because
they are still manageable by a single person to be designed and built up 
from the ground. For daily work I use
PCs or Macs or alike, but the small system is fun and hobby. I'll never 
load a modern MS-Word file into such
a system, therefore even 256k would be too small. My diploma thesis in 
the eighties was typesetted on a C64.
Generations of adults played with toy trains; the relation to small but 
handcrafted computers is quite close.

> 1.25 MHZ and get the feel for home-brew other than the PC or COCO-3 
> options I had at the time.
> I did have a COCO-3 but I never did get memory or OS9-II and a HD to 
> upgrade it to a real machine.

A new design will probably contain a compact flash or SD card for 
external storage; far more space available
than required to store all available software for such systems. I have 
no scruples to deviate from the rules of purity
(thou shalt not use modern parts in old computers) there. I'm after all 
hobbyist, not curator.

Holger