Portal 2 Minimum System Requirements:

CPU - 1.7 GHz Processor

RAM - 512MB

Video Card - DirectX® 8.1 level Graphics Card (Requires support for SSE)

Windows® 7 (32/64-bit)/Vista/XP

Other - Mouse, Keyboard, Internet Connection

 

Portal 2 Recommended System Requirements:

CPU - Pentium 4 processor (3.0GHz, or better)

RAM - 1GB RAM

Video card - DirectX® 9 level Graphics Card

 

Portal 2 Mac System Requirements

Portal 2 Minimum System Requirements:

OS X version Leopard 10.5.8, Snow Leopard 10.6.3, 1GB RAM, NVIDIA GeForce 8 or higher, or ATI X1600 or higher, Mouse, Keyboard, Internet Connection