Re: The 6809 board

[Michael Black <et472@ncf.ca>]

On Thu, 26 Jul 2012, aiiadict@gmail.com wrote:

> On Thursday, July 26, 2012 4:25:49 PM UTC-7, Alex Freed wrote:
> > Just finished the page
> >
> > http://alexfreed.com/FPGApple/Mill6809/6809_board.html
>
> What runs on the 6809 for the apple II?  What is OS9?  Screenshots from 
> anyone?  Were there commercial softwares for this coprocessor?
There were two 6809 boards, the other one I can't remember the name of. 
The other one ran Flex, which I think started with the 6800 (or perhaps a 
simpler operating system with a different name was the beginning), and was 
avaailable for the 6809 "mainframes" like the GImix and the SWTP.  It also 
ran on the Radio Shack Color Computer.  It was a fairly traditional 
operating system, a means of loading things, I seem to recall one could 
run Color Computer programs under Flex with minimal modification.

OS-9 was from Microware, a multi-user, multi-tasking operating system, 
"unix-like".  When Motorola was designing the 6809, which was quite a leap 
forward for an 8bit CPU, they went to Microware that had issued a number 
of "bug" monitors for the 6800 and some sort of operating system for the 
6800, and hired them to write a BASIC for the 6809 (I can't remember that 
story, they didn't have BASIC before).  So they came up with an extension 
of BASIC, BASIC09, which took advantage of the better architecture of the 
6809 (which in fact had been intended to better run computer languages), 
and did things like allowing a semi-compile (ie it was still interpreted, 
but at a lower level than straight BASIC).

I think Motorola's intention was to sell the BASIC in ROM, the 6809 
allowed for easy coding of relocatable programs so starting points didn't 
matter; certainly Motorola did issue one ROM, with floating point code in 
it (or at least, it was in the catalog).

But Microware didnt' stop there, they came up with a whole operating system.
If you had extra I/O, you could have mult users and it could multitaks 
(useful for sending something to the printer in the background, though on 
the Radio Shack Color Computer, serial was done in software and it was 
amusing to watch another screen while things were being printed, the 
software uart slowed things down so much that you could see the cursor 
moving over the screen).  The OS allowed for redirection and pipes, and 
was very modular, making it easy to add drivers for new hardware.

But you had to code the programs to be relocatable, so you couldn't use 
existing programs.  You could get C for it, if you were willing to spend 
the money.  Things were really cheap on the Radio Shack Color Computer, 
which may have been the biggerst base of OS-9 users.  You could get OS-9 
for just under a hundred dollars (Canadian) in 1984, though BASIC09 was 
separate at that point.  You did get the assembler.  I paid a hundred 
dollars for the C compiler in 1989.  By that time, the Color Computer III 
was out, which had memory management so the better version of OS-9 ran on 
it, there the user space was separate from the system state, and you could 
address up to 512K of RAM.  That version, still about a hundred dollars, 
came with BASIC09, but no assembler.

Very early on, people were talking about a 16bit 6502.  I remember an 
article in "6502" (was that what it was called?  Or was it "Micro"? the 
one out of Chelmsford, Massachussetts) that discussed it, it almost seemed 
like some insider piece anticipating a 16bit version of the 6502.  That 
time came and went, so the 6809 was seen as the "natural" upgrade, though 
eventually the 65816 came along.  The 6809 had an 8bit databus, but did 
some 16bit internal work, there was even a hardware multiply in there.

So everyone seemed to have a route to the 6809.  The "mainframes" jumped 
early, there was a single board computer that was like an improved KIM-1 
from Synertek, it eventually came out with a 6809 version.  All the 
magazines that covered the 6502 eventually started covering the 6809 and 
the computers that came along with it inside.


> Where is the manual? >
> A coprocessor sounds neat, but I've yet to see any useful examples of 
> software running on them.
It was more like replacing the 6502, just like the Z80 board took over the 
6502.  In some other computer, you would have unplugged the 6502, plugged 
in a "daughter board" that included the 6809 and logic ICs to adapt it to 
the 6502 pinout.  Since the Apple II had a bus, that was an easier route.

I didn't think anyone used the 6909 to run some programs, it was seen as a 
cheap way to get a new CPU, and run them under a new OS, Flex or OS-9.  It 
wasn't like a Dtack-grounded board that initially was about running some 
math code on a faster CPU.

  Michael