[Coco] FPGA the future of coco?

Mon Sep 15 17:12:18 EDT 2014

Hi Guys!
A guy named James Moxham in the N8VEM google group has designed an interface
PCB for the Altera Cyclone II FPGA Mini-Development PCB that is mentioned on
Grant Searle's Multicomp Web site which I have used to build my own
Multicomp Microcomputer which incorporates all of Grant's design onto one
board with 512KB of static ram instead of 128KB.  The FPGA simply plugs into
the PCB from the bottom.  Here is a link to a picture of my fully functional
Multicomp Microcomputer!
https://www.dropbox.com/sc/0dtg2r8cr9v36fw/AADuKsKB1GeLW8lvWUsCN53ha
So far I have compiled the 6809, Z80 and 6502 versions of the Multicomp from
Grant's web site as is and played a little with each one to get started.
Then I decided I wanted to get the SD card operating with some type of
virtual hard Disk Operating System and since the only one being developed at
that time was CP/M 2.2 running on the Z80 Multicomp, that is what I began
with.  Since that time Cubix has been ported to the 6809 Multicomp which I
will be looking into.
Now I have a Z80 Multicomp Microcomputer running CP/M 2.2 in 64KB of ram.
All the ram is available, but in 32KB blocks.  Another guy developed a 4KB
Block MMU VHDL component for the Multicomp that still another guy named MAX
is using to get CP/M 3.0 and a version of MP/M up and running with all three
OSes on the same SD card in separate partitions.
My next move is to install the 4KB Block MMU into the Z80 Multicomp and get
it working with CP/M 2.2.  Of course CP/M 2.2 won't be using the MMU, but
the 64KB would still work fine.  Once that is done, I want to try my hand at
porting the VHDL code for the MMU over to the 6809 Multicomp and try
changing it into an 8KB block MMU.  Then I want to continue my idea to
progressing on toward developing or using someone else's VHDL for the rest
of the Coco 3 and eventually end up with the Coco 3 in VHDL in an FPGA chip.
At some point I will have to move to an Altera Cyclone III or IV FPGA chip
as the Cyclone II only has about 14.25KB of memory and more memory will be
needed along with more logic elements as well.  
The Cyclone III has 50.25KB of memory which would be more than enough to
hold the 32KB rom image of the Coco 3.  Resources needed by the VHDL code is
of course not known yet as the rest of the Coco 3's functions have not been
written in VHDL at this time.  I do have available to me a Coco 3 Extended
Basic in 8KB of rom space running in the 6809 Multicomp with all the
Cassette, Graphics, Sound and Joystick commands removed as the hardware for
those functions didn't exist.  Unfortunately since Grant only had 8KB of
memory allotted for the rom image in the FPGA chip, the PRINT USING
statement had to be removed as well which brought the 6809 Extended Basic
down from 16KB to 9KB and then finally to 8KB for the 6809 Multicomp.  
How exactly to implement the rest of the Coco 3 is up in the air at this
point.  Gary Becker has graciously given me a copy of his source code for
his Coco3FPGA project, but since it is in Verilog I will have to figure out
how to integrate the parts I need for my project.  I expect I will have to
adapt the Verilog code to the Multicomp Cyclone II and ultimately the
Cyclone III or IV chips' features to get the Coco 3 in a Cyclone FPGA chip
dream of mine realized.
Well, that is my plan anyway and now you guys know about it.  If anyone is
interested in this venture, I sure could use some help with this project as
I am quickly delving into territory that I have never been involved in
before, but I am having loads of fun trying to figure all this stuff out!
Long live the Coco 3 in whatever form it ends up taking.  Take care my
friends.

Kip Koon
computerdoc at sc.rr.com
http://www.cocopedia.com/wiki/index.php/Kip_Koon
http://computerpcdoc.com/

-----Original Message-----
From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of
nickma2 at optusnet.com.au
Sent: Sunday, September 14, 2014 9:44 PM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] FPGA the future of coco?

Wow! the EP2C5T144C8N board is only $14.95AU on ebay!

That a pretty good basis for a CoCo3 FPG design. Just add a daughter card
with the required I/O. 

This is compatible with the DE1 board?

I know it may not be the perfect solution and that there may be more
powerful FPGA boards, but the price sure is a good start.

Nick 

----- Original Message -----
From: "CoCoList for Color Computer Enthusiasts" 
To:
Cc:
Sent:Sun, 14 Sep 2014 12:28:28 +0200
Subject:Re: [Coco] FPGA the future of coco?

 Am 13.09.2014 um 23:43 schrieb Al Hartman:
 > Here's a simple 6809 computer that even uses a modified Coco BASIC.
I doubt it
 > would take much work to make this into a Coco 2 clone, and then add
support for  > modern peripherals on board.
 >
 > http://searle.hostei.com/grant/6809/Simple6809.html

 Grant Searle has also a FPGA project:

 """
 Pick-and-mix to create your own custom computer on a low-cost FPGA board
(BASIC, Z80, 6502, 6809, internal/external RAM, serial/keyboard+monitor,
SD-card  for CP/M or other storage)  """

 see: http://searle.hostei.com/grant/Multicomp/index.html

 Mfg.

 Jens

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