Date   : Mon, 16 Apr 2012 17:27:30 +0100 (WET-DST)
From   : BBCMICRO@... (Peter Coghlan)
Subject: MODE 7 video corruption

>
>On the video they appear horizontally aligned in the character
>positions, but vertically aligned at varying distances within
>each character position, and (possible because of persistance of
>vision) appear in all columns across the screen, gradually going
>diagonally upwards towards the right across every character row.
>
>ie, as though the cursor is in:
>column 0, raster line 19, column 1, raster line 18.5, column 2, raster
>line 18, column 3, raster line 17.5, etc.
>

That would seem to suggest that whatever their origin, they are not characters
that can normally be displayed in MODE 7 and that further strengthens the
theory that they do not result from a memory or data bus fault. Anything wrong
in memory could only result in valid MODE 7 characters being displayed, even if
they appear where they are not wanted.

Regards,
Peter Coghlan.