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

[gene heskett]

On Saturday, November 20, 2010 11:37:45 am Mark McDougall did opine:

> On 20/11/2010 9:54 AM, Frank Swygert wrote:
> > 1. CoCo3 compatibility. Drop CoCo 1/2 semi graphics and artifacting
> > modes.
> 
> No. Don't "Drop Coco1/2...". At the very worst, simply recommend but
> don't *mandate* compatibility.
> 
> > 5. Higher res graphics that are easy to program. Something standard --
> > maybe just 640x480 VGA.
> 
> 1920x1200 is no more difficult - and requires barely more resources -
> than 256x192 in hardware.
> 
> The real problem that everyone has missed here is how you're going to
> map a huge chunk of video memory into the 6809 address space, and how
> you're going to move any decent portion of the screen around in real
> time.
> 
And that is entirely impractical, Mark.  IMO, what we should do in the 
coco1/2 mode is exactly the gfx modes the 6847 could muster and no more.

But for coco3 mode, then I see nothing wrong with a 32 bit wide path from 
the gime emulation into a full 32 bit address space in the memory. With the 
same palette abilities, then a 1920x1200 does become a workable system 
assuming there are empty spaces in the gime's mode map.

Expanded palette abilities would no doubt slow it down but we have 100x the 
clock speed to play with, so I don't believe that s/b a working target for 
'first silicon' in the fpga, at least till the thing is working within that 
framework with everything multivue can do.  However, I believe that os9 
should not be tasked with the management of that screen memory, the gime 
should hard partition it to some point above the first 2 megs that os9 with 
the 2 meg patches would know about.

Is this not something that can be hidden on the far side of the gime 
emulation & only the gime knows about it?

As for the licensing concerns, yes, this MUST remain open, with the fpga 
images freely available to everyone, some of which may have the knowledge 
to further improve it.  There are several suitable licenses but GPL3 makes 
more sense to me.

My $0.02.

-- 
Cheers, Gene
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