[Coco] What would a CoCo successor have to have as a minimum?

[Mark McDougall]

On 22/11/2010 8:58 AM, Aaron Wolfe wrote:

> this makes me wonder, should a "coco 4" just use a different or
> additional processor?
> since our targets are fpga and emulators, we aren't really tied to
> processors that exist in silicon.  we could add a 68000 or create some
> sort of hybrid 6809/68k type of thing.
> probably a lot of work, but sounds like it would be difficult to see
> significant improvements to graphics if we don't change something in
> the architecture.

My original point was not that we can't improve the graphics, but rather 
that there needs to be some consideration of the implications, and not just 
throw around resolutions just because "we can".

A video controller in HDL is just a bunch of counters. Whether 320x200 4 
colours or 1920x1200 32-bit colour is neither here nor there. We just need 
to be sensible about it.

I guess a very rough example specification would be that a 12x faster 
processor could handle 12x the graphics data of the Coco 3.

But I'd also concur that some sort of graphics processing/acceleration as 
you suggest is a good idea. 2D, 1-pixel scrolling is a start (and trivial to 
implement in a HDL). Sprites are another. I'd even go as far to suggest a 
'tilemap' layer to complement the bitmap layer(s) and sprite layer. And 
blitter (DMA). Though these are straight-forward to implement, there are 
some technical issues to overcome, such as system memory bus architecture.

All this would further increase the graphics that could realistically be 
supported by a given processor.

A good example of these types of capabilities is the Yamaha TGV608 graphics 
'coprocessor' found in the Namco Classic arcade games (I have the reference 
manual for it, and implementing that would kill 2 birds with 1 stone for 
me)! The Neo Geo arcade is also a fantastic example of what you can do with 
a tilemap/sprite system, which was still pulling the crowds well into the 3D 
era.

I don't think we need to add another CPU into the mix. An accelerated 6x09 
with the above graphics capabilities is adequate for arcade-quality games 
(after all, some actual arcade games only had 1 or 2 6809s in them, and 
we're talking about a 25MHz 6809!!) I can only imagine what Steve Bjork 
could do with such a system!

Once you throw away the 6809 then you're not talking about a Coco 4 any more 
IMHO. A 68k with enhanced graphics is called an "Amiga".

Regards,

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