[Coco] Any news on the so called CoCo4 or NextCoCo projectthatBjork was heading?

[jdaggett at gate.net]

Mark

I understand all that you have written and appreciate your imputs. 

First off I have to consider my needs since there is no concise direction for any hardware. I 
have my own needs. I will share them with the community and f there is interest then fine. If 
not that to is fine. At least for my needs, I need small. Stacked boards fits my needs. Trying 
to do it in a single board may not be small enough for my needs. I may still be able to do it in 
a single FPGA. Though it will have to be in a PQ208 package to meet all the IO needs and 
LUTs needed. BGA is out of the question. I want to stay with 2 layer boards. I do not want to 
go to 4, 6 or 8 layers. PCB costs go up considerably. i also want to stay away from gold 
plating of any kind. 

just my thoughts
james 




 

On 18 Nov 2010 at 7:52, Mark McDougall wrote:

> On 18/11/2010 2:47 AM, jdaggett at gate.net wrote:
> 
> > One suggestion that I would throw out that has already been suggested.
> > Instead of one board do all have several boards that plug into a main
> > board.
> 
> I'm going to have to disagree with this one. In fact, I would argue that it 
> is *almost* a step backwards to the days of discrete chips.
> 
> There are three problems I can see with this approach.
> 
> 1. Connectivity. Any time you take signals off-chip you're constrained by 
> the physical circuit and I/O count that have been designed into the system. 
> You actually *lose* flexibility because you can't arbitrarily connect any 
> two parts of the system.
> 
> 2. Speed. Moving data on/off chip slows things down, not only in terms of 
> raw clock rate, but also the fact that you need to shuffle data across in 
> organised bus protocols. Even more-so when off-board connectors are involved.
> 
> 3. Cost. Several boards with several FPGAs will always be more expensive 
> than a single board with a single FPGA.
> 
> I can see what you're trying to do - future-proof the design in terms of 
> expandability. But that's very difficult to do - I'd even argue impossible - 
> the way technology moves so quickly.
> 
> It's more difficult than you would think to simply connect two (different) 
> FPGAs together these days. With both core and I/O voltages changing and 
> coming down all the time, it becomes a nightmare of multiple power rails and 
> level translation. As well as the obvious cost implications, this also 
> further reduces connectivity. Trust me, been there.
> 
> I would argue that it's not difficult to predict the medium-term 
> requirements of a Coco4 project. You can get FPGAs now large enough to run 
> several complete Coco3FPGA instances at once in parallel. Once you've 
> implemented the CPU, there really isn't much that consumes a lot of 
> resources. Add the obvious I/O - VGA, PS/2, USB, SD/MMC, some sort of 
> joystick interface, some sort of network, sound. Then add 1 or 2 expansion 
> connectors for cartridge port (extremely expensive to add) and maybe legacy 
> floppy (again, expensive to add for dubious gain).
> 
> That'll do anyone for years to come. Beyond that, re-spin the board when the 
> time comes. It's likely that technology has moved along far enough that 
> it'll be cheaper than trying to expand the original design - smaller, faster 
> FPGAs with different power requirements, new media/bus standards, new video 
> standards, etc.
> 
> And it's not as if the Coco4 project evolves particularly quickly! ;)
> 
> Just my $0.02 worth...
> 
> Regards,
> 
> -- 
> |              Mark McDougall                | "Electrical Engineers do it
> |  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"
> 
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