PlayStation 4 installs are mandatory, but you could be playing the game almost immediately after whacking the disc in.
Although install times will vary from game to game, lead system architect Mark Cerny told Kotaku that Knack, the game he created for launch, is playable "tens of seconds" after beginning the install.
Speaking to Polygon, Guerrilla Games managing director Hermen Hulst said that Killzone Shadow Fall takes less than three minutes to get started after you insert the disc - 2 minutes 44 seconds, in fact, including introductory cinematic and profile creation.
"The experience when you have a disc and you put it in the PlayStation 4 is so much more seamless compared to that of current-gen gaming. There's no more loading screens between levels, and I think that's a massive technical achievement. When we commenced this project, we actually weren't convinced it was going to be possible," he said.
Cerny gave Kotaku an overview of how the system works PS4 review event in New York last night. The PS4 begins caching a disc as soon as you put it in the console, saving a varying amount of data to the hard drive. When this amount is smallish, as with Knack, you can leap in to playing really quickly - and as you do, the console will continue with the rest of the install, for parts of the game you're not ready for yet.
Knack's mandatory install is 37GB; this is noted on the game's box. When you buy a new game you should check the figure against your available HDD space and consider if you have any older games you might like to uninstall; the PS4 won't auto-delete old install data, a decision Cerny says Sony made consciously.
Installs mean games will load faster, reducing wait times, Cerny said, and the console is not designed to stream off discs.
The PS4 launches on November 15 in North America, and in Europe and beyond on November 29.