Date   : Sat, 04 May 1996 17:05:37 +0100
From   : Mike Tomlinson <mike@...>
Subject: Re: Monitor

In message <1ED652B7438@...>, Andrew Paul
<a.a.paul@...> writes
>I was going to use an olivetti monitor with my electron some time 
>ago...I asked some questions about it here... but I no longer have 
>that monitor. I do, however have a useless computer with a built in
>mono monitor.  I've managed to get the electron's picture on the 
>screen but there is a fair amount of flicker and the text is repeated 
>halfway across the screen, as I type this wraps across to the other 
>side.  I am assuming (but I'm far from certain) that the second image 
>is caused by the interlace on the electron, so can anyone suggest a 
>way of either bringing the two images together, or getting rid of the 
>interlace.  I know there is an *FX call to do this with a BBC but it 
>doesn't work on the elk.
>
>If anyone can help I'd be most grateful.
>
>
The Beeb will work with most PC compatible CGA monitors if you buffer
and feed the monitor with the separate Hsync and Vsync signals on pins
39 and 40 of the 6845 CRTC chip. They may need inverting - I can't
remember, but the composite sync output on the RGB connector of the BBC
is unsuitable. If I remember correctly, the Electron doesn't have a 6845
- it's emulated in the ULA.

I doubt the flicker/wraparound on your monitor is caused by interlace,
more likely the monitor is incompatible. Your mention of "two images"
suggests to me that it may be a VGA.

Colour Microvitec monitors for the Beeb and Elk are available very
cheaply secondhand at about ukp35, and I suggest one of those would be a
better option than farting around with a PC screen.

-- 
Mike Tomlinson
constructive email to mike@...               ; flames to /dev/null.