[Coco] CoCo4! 50% done!

[Mark McDougall]

On 11/02/2014 10:56 AM, iggybeans at comcast.net wrote:

> Right now I have the OpenCores code for the
> MC6821 PIAs, and was considering whether it was worth trying to duplicate
> Gary's efforts (its a monstrous undertaking). Also, the 6809 core Gary
> uses could definitely use some work. Right now its not even close the
> cycle exact and has none of the 6309 enhancements. And ideally, a new CPU
> core would go even further than those two goals.

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.

> Since there has been some work already done on it, one thing I'd like to
> see is a Sprite Graphics generator added to the VDP. A hardware cursor
> generated with this would definitely simply cursor movement. Many other
> possible enhancements could be considered.

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!

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"