[Coco] CoCo 3 68000/RAM board project

[jdaggett at gate.net]

All are good ideas.

Considering that the GIME has limited video capabilities, enhancing the 
graphics ability of the GIME chip you eliminate the second 6809 to do 
graphics This can be done by building into the new GIME a graphics 
processor that takes commands and draws the polygon and line shapes 
within the configurable graphics window. 

I lean to more enhancing the graphics capability of the GIME chip over a 
dual processor 6809. Unless you have OS9 modified to handle dual 
processors, a coprocessor makes better since with enhanced graphics. Also 
consider this, a FPGA based system can be made to run considerably 
faster than the current Coco3. About ten times faster. 

james

On 8 May 2009 at 22:17, 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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