Thanks to everyone for their insights.

OK, can ANYBODY tell me what the OS size on the Yamaha PSR9000 and 9000pro are? I would assume they aren't much more (if at all) than 1.4mb , especially if they're user OS ROM upgradeable via floppy disk(s).

If this is true, there definitely is something very different about the design of the Tyros keyboard in this regard. What EXACTLY is filling up that additional 38 MB on the Tyros? is it the new Mega Voice sounds? I would think the sounds to be better stored on IC chips, not in Flash Rom. I hope a logical answer is forthcoming from Yamaha. I'll keep you posted if I hear privately.