I found this on internet and..... This can't be right.

Minimum requirements:

OS: Windows Vista, Windows 7 or Windows 8
Video: VGA compatible with DirectX11 and at least 1Gb VRam
CPU: CPU with 2 cores de 2,4Ghz
RAM: 2gb (3gb for Windows Vista)

Exemple 1 (nVidia/Intel):

nVidia GTS 450
Intel Core2 Duo 2.4 ghz (E6600)

Exemple 2 (Amd):
Amd Radeon hd5770
Amd Athlon64 x2 2.7 ghz

Recommended requirements:

S.O: Windows Vista, Windows 7 or Windows 8
Video: VGA compatible with DirectX11 and at least 1Gb RAM (nVidia GTX560+) (AMD Hd5870+)
CPU: CPU with 4 cores 2,4ghz
RAM: 4Gb

Exemple 1 (Nvidia/Intel):

nVidia GTX 560
Intel Core i3-530

Exemple 2 (Amd):
Amd radeon hd5870
Amd phenom ii x2 565

For maximum performance:

Windows Vista, Windows 7 or Windows 8
Video: nVidia serie 600 or Amd serie 7xxx
CPU: CPU with 4 cores, last models
RAM: 8gb

Exemple 1 (Nvidia/Intel):

nVidia GTX 680
Intel Core i7-2600k

Exempe 2 (Amd):

Amd radeon hd7970
Amd bulldozer fx4150

Sorry if it looks weird, I had to translate from Portuguese to English.

Font: http://www.gamevicio.com/i/noticias/146/146217-divulgado-os-requisitos-para-crysis-3/index.html