I have some understanding of this being someone who has installed way too many aftermarket head units, and as best I can tell, all the rendering indeed occurs on the phone. The CarPlay experience is virtually identical across all the units I've tested on, from my stock '18 Corvette unit, through 4 or 5 ones I've shuffled through in my F-150, and through 2 or 3 through my Chrysler 300. Apart from display size and density, there is no difference at all in all these CarPlay units. They function identically.

The phone also gets notably warm even just playing music which is part of why I strongly suspect all of that is phone-side activity at play with the dash just providing a resolution/density combo and touch inputs.

> Would they implement an entire backup dashboard for this?

Correct, if my research is to be believed. There's a stock OEM OS look to everything in line with each brand's visual designs, which is then swapped out to whatever degree they feel like exposing to CarPlay Ultra, at which point it's reskinned in Apple's look.

I don't own any vehicles new enough for this, but it's pretty cool if it works. That said I'm less a fan of everything being a display. For gauges and such I do prefer physical gauges.

For efficiency's sake, I hope it's like a theme (in the style of Winamp, or well, Windows XP), so you can pick some theme on your phone, and the phone tells the car to use that theme while rendering the car's instruments. For UI elements needing data from the phone (like album cover image), the theme would tell the car computer to fetch it from the phone. Considering the state of the tech industry, it's probably HTML and CSS too. And Javascript. Goatse anyone?

By the way... who the hell thinks it's important that someone operating a 800+ horsepower car should be able to be distracted by what the album cover of the music currently playing looks like..?