"a HD DVD accessory was required to play HD DVD content on the xbox 360." Once again demonstrating the murderously huge difference between hardware that ships

"a HD DVD accessory was required to play HD DVD content on the xbox 360." Once again demonstrating the murderously huge difference between hardware that ships with the platform and attempts to add on hardware to the install base later. Exceptions will leap to mind, like the rumble pack for the N64 or the Dualshock controller, but in general, add-on attempts fail and fail miserably for gaming consoles. They don't leap to mind precisely because they failed.