Date   : Mon, 16 Apr 2012 18:07:41 +0000
From   : jackleather@... (jack leather)
Subject: MODE 7 video corruption

thanks for all the help so far!

i will digest everyone's wisdom and take another look.

also i have just noticed that the keyboard input has gone weird again. some
keys result in the wrong characters. 
This was the original reason why i swapped the user and system VIA's and
it solved the keyboard problem but only temporarily it seems.
This means i cant enter any of the BASIC commands/programs you have posted.

Hmmmm...



> Date: Mon, 16 Apr 2012 17:27:30 +0100
> From: BBCMICRO@...
> To: bbc-micro@...
> Subject: Re: [BBC-Micro] 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.
> 
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