OK, I can now confirm that the nVidia FX5200 will generate the 405 line timings
With a huge amount of help from Kat
, I've got a KnoppMyth system built and running, and have managed to load the correct modeline (thanks again Kat!), and as I type this, the 'scope is displaying correctly timed synch pulses.
All I have to do now is build the hardware, and finish repairing my 405 line sets
Jim.