[Coco] CoCo4! 50% done!

[iggybeans at comcast.net]

>Message: 10 
>Date: Tue, 11 Feb 2014 12:15:31 +1100 
>From: Mark McDougall <msmcdoug at iinet.net.au> 
>Subject: Re: [Coco] CoCo4! 50% done! 
>To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com> 
>Message-ID: <52F979B3.5040601 at iinet.net.au> 
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed 


>FTR, recreating the Coco3 is nowhere near as complex as rewriting the 6809 
>core. So if you want to start somewhere, I'd look at a new Coco3 before 
>attempting a new core. 


>As I mentioned here recently, and it appears to have been all-but-ignored, I 
>am aware of a rather accomplished FPGA designer who has recently been 
>working on a 6808 implementation, and has plans to extend it to 6809/3 at 
>some point. No word on ETA at all unfortunately. 


Yes, a more accurate 6809 core would be difficult, a 6309 core even harder, 
and an enhanced version of the latter would be an enormous endeavor . 
But an enhanced processor would be so nice to work with. 
Just the improvement that could result in an improved interrupt vector system alone intrigue me. 
And, what would a fully 32 bit 6309 look like? 


>IMHO the bitmapped graphics of the Coco3 would be perfectly complemented 
>with a simple scrolling tilemap and sprite engine. They're actually rather 
>trivial to implement in an FPGA, but offload a lot of work from the CPU and 
>would enable some pretty cool platform and shooter games! By the same token, 
>adding 2D pixel scrolling to the bitmap wouldn't go astray either! 


Those sound like relatively easier goals. 
Enhanced sound, better A to A and A to D resolutions, an enhanced MMU and 
DMA would not hurt either. 
A Sprite layer similar to that included in the F-18A FPGA should be possible. 
And increased on screen colors would make sense.