[Coco] Why do we need a CoCo 4? (Long irrelevant rant)

[Joel Ewy]

Frank Swygert wrote:
> Am I reading this right? Could a more or less CoCo compatible machine
> be made with a HC12? Something that would be at least 75% compatible? 
Not quite Frank.  The issue here is that the HC12 lacks the U(ser) stack
pointer register.  That's a pretty major omission. (Nitr)OS-9 would be
right out, and I suspect that DECB uses U as well.  It's an "if only",
but a pretty big "if only".

JCE

> I know that a lot of compatibility issues with the CoCo 3 are in the
> GIME chip, but you're working that issue! Of course I'd like to see
> something backward compatible with DECB, but I think it should be
> acceptable if CC1/2 compatibility suffered or was gone (such as
> support for PMODE screens) IF the space were needed for graphics
> enhancements or coding could be seriously simplified. There would be
> some software "loss" without those old graphics modes, but I
> personally think that would be an acceptable compromise -- can't be
> many "popular" programs out there that don't have some newer CC3
> replacement. Some of the kids games, most likely, would be lost. DECB
> could even be patched if necessary. As long as CC3 specific games ran
> I don't think many would object.
> ------------
> Date: Mon, 29 Dec 2008 20:41:32 -0500
> From: jdaggett at gate.net
>
> Probably would be better to do something like what the HC11/HC12
> approach. Then again if the HC12 had a U register then this thread
> would be mute. A Coco4 would better be done with an HC12.