How the hell have Rockstar managed GTA V on 8 year old hardware?

Seriously apart from one or two streets on los santos with lots of palm trees on it this game absolutely purrs along, the lighting is gorgeous and attention to detail insane , there are no in-game loading times and hardly any pop up all with this with an extermely stable framrate. The only gripe I would say are jaggies but this is a minor complaint. it blows my mind that this is on hardware older than my 7 and a half year old cousin, a great love letter to both the Xbox 360 and PS3

We've got a big thread going for the game here.