Date   : Fri, 10 Dec 2004 15:55:14 +0000 (GMT)
From   : Tom Walker <tommowalker@...>
Subject: Re: Video ULA shenanigans

> When we say "40-character" we're referring to the
> number of characters 
> per line the TT chip generates. Firetrack does
> something weird with the 
> CRTC chip. Its still 40 characters wide, but the
> sync pulses are in 
> weird places causing the display to wrap. Quite why
> the TT is happy with 
> this I do not know, I would expect it to screw up
> completely.

You sure? I was just experimenting with my BBC, and I
was able to convince the TT chip to show more than 40
characters by only changing CRTC R1 - all the sync
registers were left alone.
 
> Firetrack then uses custom routines to work out
> where to display things. 
> And IIRC, it was less than 40 characters.

50x18.

If anyone is still interested, setting the ULA to high
clock teletext generates a teletext display with every
other character skipped.

Tom


               
___________________________________________________________ 
Win a castle for NYE with your mates and Yahoo! Messenger 
http://uk.messenger.yahoo.com