Date   : Fri, 19 Dec 1997 14:11:00 EST
From   : "Arlen Michaels" <amichael@...>
Subject: Re: How do I make Beeb video stable on 60 Hz?

In message "Re: [BBC-Micro] How do I make Beeb video stable on 60 Hz?", 
'mike@...' writes:

>In article <199712161656.QAA01508@...>, Arlen Michaels
><amichael@...> writes
>
>>Can anyone help with this one?  My BBC Model B makes a slightly jittery
>>display when I connect my RGB monitor.  The Beeb was originally used in
>>Scotland but now I'm running it here in Canada where we have 60 Hz mains
>>power, and I suspect there's a 50 Hz timing dependency that I've got to
>>change. Is there a software or hardware patch I need?
>
>The mains frequency won't make any difference when running on a RGB
>monitor.  What you are probably seeing is the Mode 7 interlace, which is
>worse on some monitors.  Some top-of the range CGA monitors even had a
>control to reduce the jittery effects caused by interlace.  If you type
>
>*TV 0,1
>MODE 1
>
>does the jitter stop?
>
>You can turn off interlace in Mode 7 with the following:
>
>VDU 23,0,8,144,0,0,0,0,0,0,0,0,0,23,0,9,9,0,0,0,0,0,0,0,0,0 
>
>but that spoils the nice rounded Mode 7 font.
>
>-- 
>Mike Tomlinson
>

Thank you Mike, I will try this.
Arlen