Which design allows a 64-bit operating system to handle more RAM efficiently?

A 64-bit operating system is specifically designed to manage larger amounts of RAM compared to a 32-bit system, which is limited to addressing a maximum of 4GB of RAM. The design that allows a 64-bit operating system to handle more RAM efficiently is synchronous architecture. This architecture facilitates coordination between the CPU and memory, ensuring that data is transferred at higher speeds with improved efficiency, particularly as the amount of RAM increases.

Synchronous architectures leverage a clock signal to manage data transfer between components, which can reduce latency and enable the system to utilize the larger addressable memory space efficiently. By synchronizing operations, it enhances performance and optimizes how the operating system and hardware interact when managing larger datasets.

Other options like SMRAM, DIMM, and DDR, while related to memory technologies, do not fundamentally represent the design method that governs the overall efficiency of RAM handling in a 64-bit operating system context. DIMM refers to a type of memory module, DDR pertains to the technology of memory data transfer rates, and SMRAM is a type of memory used for storing system management interrupts but does not specifically address the efficiency of RAM handling by an operating system.