Ah OK, I had no idea that a hardware mod was needed. I've been puzzled by the hi-res stuff ever since I saw 'forty niner' and while I had a 32K '81 on the bench I thought I'd give it a go. In one of those forum postings you link to I note that the DIY internal 16K mod is hi-res capable so I'll dig out my 'exhibition' machine which I upgraded so I didn't get constant RAM Pack wobble when the machine was being moved around by excited kids.
At least the Frankenbeast is now ready for exhibition at the Centre For Computing History's annual Retro Weekend in Cambridge in September
Might need to get a back porch generator for it though. Now that I know the machine itself works I may re-hook up the odd video board and see if I still get a broken picture.
