[Coco] CoCo 2 16k.. Upgrade or no?

[Darren A]

On Wed, Mar 14, 2012 at 3:44 PM, William Astle <lost at l-w.ca> wrote:
>
> There's still a wasted byte related to setting the top of the stack pointer.
> When it sets S, it should set it to the address of the last free byte of RAM
> plus one rather than to the last free byte of RAM since pushing onto the
> stack is a pre-decrement operation. (In other words, the stack pointer
> should start out pointing to the lowest address byte of string space.)
>
>

I always figured that the reason Color Basic has the one wasted byte
is because of an oversight when the code was adapted from the 6800
version of Microsoft Basic.  The 6800 has a post-decrementing stack
pointer.  The ROM code in the MC-10 works the same way, but because it
has a 6803 cpu, it needs to initialize the stack pointer to point at
the last byte of RAM rather than just past it.

Darren