More news. It gets weirder.

I moved the card back to a 64-bit slot. I used a kernel that eliminates
the use of vga_copyrows and sets dispoffset to 0, as described to
someone else.

Now I get, while the kernel is still configuring, that the screen
changes from a normal text screen to a pettern with vertical stripes...

Maybe I should set dispoffset to 0x18000 as used in vga_common_probe?
on the other hand that value is wildly out of the rance [0, 0x8000 -
type->nrows * type->ncols * 2) which is used in vga_init_screen.

More experiments will follow... maybe it's not the scrolling but the
colour attributes or something...

-Olaf.
--
___ Olaf 'Rhialto' Seibert - rhialto@polder.ubc.     -- If one tells the truth,
\X/ .kun.nl     -- one is sure, sooner or later, to be found out. (Oscar Wilde)