HP A2Z48AT, 4 GB, 1 x 4 GB, DDR3, 1600 MHz, 240-pin DIMM HP A2Z48AT. Internal memory: 4 GB, Memory layout (modules x size): 1 x 4 GB, Internal memory type: DDR3, Memory clock speed: 1600 MHz, Memory form factor: 240-pin DIMM, ECC