Date   : Mon, 15 Oct 2007 23:22:28 +0100
From   : public@... (Daniel Beardsmore)
Subject: Video ULA compatibility query

I imagine most Beeb fans will be aware that the original Ferranti video ULAs
on the Issue 4 and earlier would cook themselves and end up displaying all
sorts of weird visual defects like snow, stripy colours, bad default palette
entries (entry 3 in mode 2 showing red instead of yellow) and just general
garbage on the screen.

My first ever Beeb had this, and when I'd sold it to my cousin I later tried
replacing the Ferranti ULA with a VTI 2069 from an Issue 7. While modes 0-6
were fine, it seemed to be incompatible with the SAA5050 causing Teletext
text output to be horribly smeared on his colour television and barely legible.

I'm presently running an Issue 4 that also had a fried ULA, replaced again
with one from a (broken) Issue 7. I have no TV; I'm using a Microvitec Cub
screen and mode 7 displays perfectly.

According to Jon Ripley's Wiki that led me here, the VTI VC 2069 is a
straight drop-in replacement for the Ferranti predessor, but clearly
something changed between the Issue 4 and 7 that makes the VC 2069-based
ULA, or the software therein, incompatible somehow. I'm just curious as to
whether anyone knows what this is about?