This 4Gb chip is designed to operate at up to 1.6Gbps with just 1.35V of juice, nicely below the 1.5V standard for DDR3. If I have my math right, that 1.6Gbps should translate to operation at 1600MHz—in line with high-end DDR3 modules available today.
Samsung says its 4Gb chip allows for 8GB unbuffered DIMMs for regular PCs and 16GB RDIMMs for servers. Memory makers can already produce 16GB modules using 2Gb chips, but they need 64 chips to do so instead of just 32, as they would with the 4Gb chip. DIMMs made with fewer chips should consume less power. Also, Samsung says that with dual-die packages, its 4Gb chips can be used to make 32GB modules.