HP Z820 Xeon E5-2660 8 Core 2.20GHz 20MB cache 1600MHz 2nd CPU. Processor socket: Socket R (2011), Processor clock speed: 2200 MHz, Processor front side bus: 1600 MHz. Maximum RAM supported: 750 GB, Supported memory types: DDR3-SDRAM, Supported memory clock speeds: 800, 1066, 1333, 1600 MHz. Thermal power: 95 W, VID Voltage Range: 0.6 - 1.35 V. Tcase: 73 °C. Compatibility: HP Z820