[Coco] Multi-Processor 6809 Computer System

[Gene Heskett]

On Wednesday 01 May 2013 10:08:00 Brian Blake did opine:

> Would a newer, faster, better CPU be useful without also improving the
> capabilities of the GIME? If the circuitry on the prototype ever gets
> decoded, and compared to an actual GIME chip, maybe a CPU/GIME upgrade
> board could be designed to solve the problems that have been discussed
> thus far.

There is a 3rd 400lb gorilla here too. Since the GIME is in charge of the 
memory access, interleaving video access with cpu access, the speeds of the 
memory would soon be found to be a limiting factor also.  Probably before 
even the 63C09's nominally 4MHZ maximum clock has been reached.  Any 
thoughts of a new GIME at 20MHZ and you are looking at replacing the memory 
with 20ns memory.
 
> I would think, since 6809 & 6309 CPU's are still available, maybe a plug
> in replacement for the GIME might be a better place to start.

Even if we did have the design decoded, and wanted to redo the GIME in 
cmos, to run at 20+ MHZ, the NRE (Non Returnable Engineering) costs at 
whatever fab house could do it, would likely be in the region of half a 
million.  So with our limited numbers to spread that cost around, obviously 
that will never happen.  The closest we will ever get practically would be 
some sort of an FPGA version with a base that fit the GIME socket, and 
which would need its own wall wart power supply.

There are so many basic hardware limits to be overcome that I don't believe 
the idea is at a practical.  The whole coco3 or 4, in one of the emulator 
boards like the DE-1 or similar 400k gate device, with an adapter that 
makes it fit the coco3 case, is a far more do-able project.  But even that 
would be a labor of love due to the startup costs and restrictions placed 
by the suppliers of such devel kits.

When this first was being discussed, I downloaded the 'starter kit' 
software from both of the vendors mentioned, finding first that it was 
married to windows and neither wine nor crossover office would run it.  
That was about 3 years ago.  They haven't even bothered to reply to my 
questions about a linux version, but they sure spent the next 2+ years 
bombarding my inbox with several times a week requests to convert my 
starter package into the full blown commercial version at prices in the 500 
to 2500 USD range.  Perhaps their support for windows users is better than 
that, but since there are no windows installs here, I'll not further pursue 
that moving target.  IMO that is their choice, and it was mine to deny the 
emails from their IP addresses so I no longer see those nagging, even 
obnoxious sales pitches.

One thing that I have discovered about the GIME in my machine, is that it 
is extremely sensitive to the voltage on its power rails.  At one point I 
noted that there were supposed to be some ferrite beads to help trap the 
noise, but on close inspection were actually 10 ohm resistors!  Located in 
a tight spot, difficult to get to, I managed to get a short jumper with a 
real bead stuck on top of the resistor.  This raised the voltage by perhaps 
25 millivolts, and made an amazing improvement in its video output, lots 
less noise. If we could turn the bus voltage up to say 5.2 volts, still 
well within the ratings of everything in the coco, the improvement in video 
output alone would be a huge improvement.

> Or maybe not, since I'm no where near an expert....
> 
> 
> Brian

And finally to Dennis, I have looked through kmails prefs again this 
morning to see if it is possible to use a signature selected by the mailing 
list I am replying to, and have come up empty, so the same sig gets used on 
an ISP account granularity.  Since I have only one email account that 
actually Just Works(TM), the best I can do is to manually edit off some of 
the content you find objections to.  I will attempt to remember to do that, 
but old habits die hard.

Cheers, Gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
My web page: <http://coyoteden.dyndns-free.com:85/gene> is up!