Date   : Sat, 04 Jun 2011 01:19:50 +0930
From   : station240@... (Paul Asin)
Subject: Model B with video corruption

Wrote this little program up to find it.

10 cls
20 for I=&3000 to &8000
30 a=?I: if a>0 then print a;" ";I
40 next

It's not perfect but found 4 to be the random value, which means D2 is the
bad data line, hence fault in IC 55

IC 55 is slighty warmer than the other RAM chips.

On 03/06/2011,@10:34 PM, "Mark Haysman" <jumbos.bazzar@...>
wrote:

> Could be other faults as well, but that screen noise is almost definately
a bad memory chip, just need to do some pokes and peeks to the CAS1 memory
range to find what one it is.
>  
> Mark.
> ----- Original Message -----
> From: paul aslin
> To: bbc-micro@...
> 
> 
> > Is the contents of the screen memory
> > wrong or is it only what is on the screen that is wrong? If the screen memory
> > is corrupt, is non-screen memory corrupt too? Is there corruption in all
> > screen modes?
> 
> I don't think its the memory itself, noise is rather odd to say the least.
> http://s1092.photobucket.com/albums/i405/station240/bad%20B%20video/
> View from 1 to 5.jpg and that is the order the noise appears in.
> Of note is this is a 20k screen mode, and the top potion is never corrupted.
By my calculations this is &3000-&3FFF. Something screwy going on with the
addressing.
> 
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