[Coco] hardware scrolling revisited...

[Nick Marentes]

John W. Linville <linville at ...> writes:

> That is somewhat true.  But without the SAM there is also no way
> to relocate the video buffer.  Both of those features are enabled
> by the fact that the VDGs address lines are completely ignored.
> The SAM controls the video RAM addressing, enabling it to fetch from
> different parts of memory and to step the addresses on different line
> boundaries than the VDG expects.

Yes. You are correct John. Without the SAM, many programs would not have
worked even if they used proper modes.

I guess it does seem strange that Tandy would incur such a ruling especially
since the semigraphics mode was the most colorful of the modes.

I have mentioned before that I have always hated the 6847 VDG because of
it's color limitations but semigraphics mode was the exception.

Apart from it's color mapping restrictions and low horizontal resolution, it
still held potential when used right. My first CoCo 1 program was Neutroid
and it was semigraphics. I specifically designed that game for the
semigraphics mode restrictions.