Memóriasávszélesség

Memóriasávszélesség is the maximum rate at which data can be transferred between memory and the processor or other components in a computer system. It is commonly expressed in gigabytes per second (GB/s) and characterizes how much information can move through the memory subsystem over time.

The bandwidth depends on several factors: memory type (DRAM generations such as DDR4/DDR5, GDDR, HBM), memory bus width per channel, clock frequency, and the number of memory channels supported by the memory controller. In practice, bandwidth also depends on the memory controller, interconnects, and how data is interleaved across channels, as well as overhead for refresh and protocol.

Theoretical peak bandwidth can be estimated as: per-channel bandwidth = (bus width in bits / 8) × data rate in MT/s. For a 64-bit channel operating at 3200 MT/s (DDR4-3200), that yields 8 bytes × 3200 million transfers per second = 25.6 GB/s per channel. In a dual-channel system, total peak bandwidth is double to 51.2 GB/s, neglecting overhead.

Different memory types have distinct characteristics. GDDR and HBM, used in GPUs, emphasize high bandwidth at the expense of latency, while system DDR memory balances latency and capacity. Real-world bandwidth often falls short of the peak due to overhead, memory protection, channel interleaving inefficiencies, and access patterns.

Measuring and comparing memóriasávszélesség typically involves synthetic benchmarks (e.g., STREAM, AIDA64) or application-based tests. It is a key factor for workloads with large sequential data transfers and impacts overall system performance, alongside memory latency and capacity.