ASUS K20DA K31DA-K31DAG BIOS 0401 Space-saving PC with super-fast connectivity Windows 8.1 or other editions available AMD Beema processors for energy-efficient, productive multitasking. NVIDIA® or AMD discrete graphics to handle most graphics-intensive tasks. Space-saving 10-liter chassis. USB 3.1 transfers data 20x faster than USB 2.0. ASUS SonicMaster audio technology and intuitive AudioWizard interface for enhanced sound. Ultra-quiet performance with noise levels below 23dB at idle.