Minimum Just Cause 3 System Requirements:

    OS: Windows Vista SP2, Win 7 SP1, Win 8.1 (64-bit operating system)
    CPU: Intel Core i5-2300 2.8GHz 2.93GHz or AMD Phenom II X6 1055T 2.8GHz
    RAM: 6GB
    GPU: Nvidia GeForce GTX 660 (2GB) or AMD Radeon HD 7870 (2GB)
    DX: DirectX 11
    HDD: 45GB

Recommended Just Cause 3 System Requirements:

    OS: Windows Vista SP2, Win 7 SP1, Win 8.1 (64-bit operating system)
    CPU: Intel Core i7-3770 3.4 GHz or AMD FX-8350 4.0 GHz
    RAM: 8GB
    GPU: Nvidia GeForce GTX 760 (3GB) or AMD Radeon R9 280X (3GB)
    DX: DirectX 11
    HDD: 45GB


(il y a ton Cpu en config mini, et ton Gpu en conf recommandée)
ça a changé à la hausse :
http://www.jeuxvideo.com/news/450790/just-cause-3-les-configurations-recommandees-sur-pc.htm