[Coco] CoCo3FPGA, FPGA Development, and GIME replacement

Leonard Miller leonard23 at verizon.net
Wed Jul 6 11:52:43 EDT 2011 

Thank you for clearing up some of my questions.  You even answered questions
that I didn't even ask yet:-)!  I wasn't so interested in games although I
do have an interest in adventure type games done up os-9 style.  I really
like the hardware approach for the present & future.  I also like the idea
that I can simply upload the file and use the board right away.  I might
even learn something along the way.

Leonard


-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
Behalf Of Joel Ewy
Sent: Wednesday, July 06, 2011 11:31 AM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] CoCo3FPGA, FPGA Development, and GIME replacement

On 07/06/2011 07:36 AM, Leonard Miller wrote:
> I have been following the discussions about the CoCo3FPGA for some time.
If
> I was to purchase a FPGA board which one should I get?  I know that the
FPGA
> boards are boards that allow the user to use software to program hardware,
> but that's about it.  I believe the guys working with this use a couple
> different boards?  This would be a HUGE endeavor on my part, but it might
be
> fun to learn something new as long as I don't get overwhelmed doing it:-)!
> > From what I've seen so far; I can use a current computer monitor, but
what
> about storage?  Can the board interface to an IDE type drive?  How do I
move
> software back and forth between what I currently have (coco3), and the
> board.  Also, what type of power supply do I need to power the board?
>
>
> Leonard
>

The two boards that can presently run CoCo3FPGA are the Digilent Spartan 
3 (which has a Xilinx FPGA) and the Terasic DE1 (which has an Altera 
FPGA).  Gary's original CoCo3FPGA design was done on the Digilent 
Spartan 3 board, and that's why I got one of those.  He later ported it 
to the DE1, and now supports both, though it seems like the DE1 has 
become more popular among users, and the recent versions have been 
released for the DE1 first.

Each board has its pros and cons.  The Spartan 3 is, I gather, somewhat 
smaller than the DE1.  I have mine installed in an old CoCo 3 case:  
http://8littlebits.wordpress.com/2010/12/18/an-old-case-for-a-new-coco/  
I believe that the Spartan 3 board has more memory than the DE1.  I 
think the Spartan has 2M of SRAM and the DE1 has 512K.  On the other 
hand, the Digilent board needs to be modified in order to display even 
the CoCo 3's 16/64 colors, with further modification required for the 
new 256 color mode and 12-bit palette.  (I think an alternate way of 
displaying the colors uses a small breakout PC board with a VGA 
connector and resistors, so you don't need to actually modify the 
original board.)  The DE1 has full support for both the old and new 
video modes built in.  The DE1 also has an SD card interface, though at 
this time it is not supported in CoCo3FPGA.  I think the price of the 
two boards is comparable -- in the $150 range.  I think the DE1 may also 
have audio circuitry built in.  Both boards require extra interface 
circuitry to interface with CoCo joysticks (and for the Spartan 3 board, 
audio out).  Gary has designed the CoCo peripheral interface boards (I 
think he may not yet have finished the re-designed Spartan board) and 
makes the schematics and PCB layout files available for free, but I 
don't think you can buy manufactured, assembled boards at this point.

I guess if you really want 2M of RAM and don't mind doing a little extra 
work, the Digilent Spartan 3 gives you more memory.

But the DE1 will probably be the easier route if you just want to plug 
it in, upload the bit file, and go.  If you want to hook up CoCo 
joysticks you're going to have to build an interface board in either case.

Both of these boards will come with a little wall-wart to power them.  
The only storage option at the moment is Drivewire, so you'll need a 
modern-ish PC with Linux, MacOS, or even MS-Windows, and Java.  And 
you'll need a serial cable or a serial<->USB adapter.  No IDE at the 
moment, but it should be possible for somebody do design an IDE 
interface for either or both FPGA boards.  If you want to move software 
or data between a 'real' CoCo and CoCo3FPGA, that can be accomplished 
with Drivewire.

One other caveat:  The 6809 implementation in CoCo3FPGA is not cycle 
accurate to a real 6809.  It runs the same instructions, but not always 
in the same number of clock cycles.  This means that some programs 
(mostly games) that rely on careful counts of the clock cycles of 
instructions for timing purposes may not work right.  So you may be 
disappointed if you just want a replacement CoCo to play games.

On the other hand, CoCo3FPGA can run at ~21MHz, has enhanced graphics 
modes, and has the equivalent of an Orchestra 90 stereo sound Pak built 
in.  Furthermore there is potential for future development, and if/when 
Gary releases the source (as he has suggested he will do) development 
won't have to cease when Tandy (or Gary Becker) decides it's not fun 
anymore.  I don't think there will ever be a mass-produced, 
shrink-wrapped Next Generation CoCo.  But if there's enough interest, we 
could very well see hobbyist-produced kits that make it pretty easy to 
plug in one of the FPGA development boards, upload the CoCo3FPGA bit 
file, and go.

JCE

> -----Original Message-----
> From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]
On
> Behalf Of Rogelio Perea
> Sent: Wednesday, July 06, 2011 5:40 AM
> To: CoCoList for Color Computer Enthusiasts
> Subject: Re: [Coco] CoCo3FPGA, FPGA Development, and GIME replacement
>
> On Wed, Jul 6, 2011 at 3:20 AM, Nick Marentes wrote:
>
>
>> There's always a version 2!!   :)
>
> I second (or third?) that!.
>
> "Design Freeze", a concept that if not followed will keep the R&D in a
loop
> never reaching (or reaching late if at all) the goal to have something go
> from the drawing board into production. Seen that happen all the time,
> unchecked it can kill an organization.
>
>
> -- RP
>
> --
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