[Coco] CoCo 3 68000/RAM board project

[mike delyea]

I'd like to see a second 6809 too.  I remember seeing some screen
shots of a Japanese machine that had 2 6809s with one cpu being used
for graphics (I think) and I seem to recall it looked pretty good
(found it - heres the link).

http://www.nausicaa.net/~lgreenf/fm7page.htm

On Sat, May 9, 2009 at 1:17 AM,  <bkheath at gmail.com> wrote:
>
>
> On Fri, 8 May 2009, Andrew wrote:
>
>>>  Message: 1
>>>  Date: Thu, 07 May 2009 10:39:47 -0400
>>>  From: jdaggett at gate.net
>>>  Subject: Re: [Coco] CoCo 3 68000/RAM board project
>>>  To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
>>>  Message-ID: <4A02BA73.21591.786DE5 at jdaggett.gate.net>
>>>  Content-Type: text/plain; charset=US-ASCII
>>>
>>>  All
>>>
>>>  The CPU module containing the FPGA for the 6809 is laid out and needs
>>>  verification. The memory module is also done. It will be a 1Megabyte by
>>>  16 10 nS SRAM. Another board could be done using SDRAM. Now the Main
>>>  board and peripheral boards are left to design and lay out.
>>>  What I am doing is shrinking the size of the main Coco board down to
>>>  100mm by 80mm size. Taking a fes of Sock's ideas also into
>>> consideration.
>>>  The CPU  FPGA will be capable of one 6809 plus room left over for a math
>>>  coprosser or a second 6809.  The GIME FPGA is also large enough to
>>> handle
>>>  VGA desktop of 800x600 pixels at 8 bit color. That is able with the
>>>  2Mbytes of ram. 1Mbyte for video desktop and at least one 640x480
>>>  hardware window. Lower resolutions can have more windows.
>>>  Coding status for the GIME chip is all the registers are done. Need to
>>> do
>>>  the video section with windowing, and the linear address generater for
>>>  the video ram access. Also the multipexor between the CPU and video
>>>  addresses.
>>>  As for the math coprosser, I have a cordic processor started. It
>>>  eventually will handle all division, multiplication and several trig
>>>  functions. I have yet to dicide wthether it will be just integer or
>>>  handle floating point yet. That will depend on how much room is left
>>>  after the core of the cordic is left.
>>>  james
>>
>> James,
>>
>> Personally, I would want to see the second 6809, 2 meg of ram, but with a
>> limit of 320x400 with 256 colors (Mode X, more or less), and hardware
>> sprites. If not a second 6809, then a music/sound chipset or something,
>> which the CoCo has sorely lacked forever, barring the SSC and/or Orc-90
>> (although I hesitate to call the Orc-90 a music/sound chipset - most of the
>> functionality was in the software, the hardware being only a very nice set
>> of DACs for stereo sound).
>
> I like the idea of a second 6809. Since you've already got an
> MMU and fast ram why not do that Motorola dual proc design with
> the two E clocks 180 out of phase. Set aside a register set in
> the MMU for "shared" blocks (which could also be none). Then
> software could configure it with one for I/O one for processing,
> or one for block devices one for user interface, lot's of
> possibilities, even independent EDB and OS9 with the shared
> memory emulating a fast comm link.
>
> 'Course I wanted to build a set-up like this back when my
> hardware bench was available, still do if the chance comes.
>
> There should be room, the CPU-CPU memory arbitration logic was
> pretty simple, though it does involve buffers to isolate another
> set of address and data lines to keep it from interfering with
> the interleaved display memory.
>
> Just some thoughts.
>
>
> Brett K. Heath
>
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