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The maximum sustained rate at which data can be read from or written to a memory subsystem.
DESCRIPTION
Memory bandwidth quantifies data throughput between processors and memory, typically measured in GB/s. It depends on memory type, bus width, clock rate, channels, and architecture. High bandwidth is critical for GPU/CPU performance in data-intensive workloads, including ML training and analytics. Techniques like HBM and multi-channel DDR increase bandwidth. Bottlenecks occur when computation stalls waiting for data. Profiling and system design aim to match compute with adequate bandwidth.
ALTERNATIVE DEFINITIONS
Wikipedia
Memory bandwidth is the rate at which data can be read from or stored into a semiconductor memory by a processor.
Focuses on processor–memory data rate definition.
Intel
Memory bandwidth refers to the sustained data transfer rate between memory and the processor, a key determinant of application performance.
Connects bandwidth directly to application performance impact.
NVIDIA
Memory bandwidth is the amount of data per second the memory subsystem can deliver, and kernel performance is often limited by it.
Warns of bandwidth-limited GPU kernels and importance of coalesced access.
RELATED TERMS
HBM DDR5 PCIe Cache Bus Width Clock Rate Throughput Graphics Processing Unit Microprocessor
COMPETING TERMS
Memory Latency
KNOWLEDGE AREAS
Infrastructure Data Storage & Operations Observability & Telemetry
TARGET AUDIENCE
Hardware Engineer MLOps Engineer Cloud Architect DevOps Engineer
EXTERNAL SOURCES
- Wikipedia - Memory bandwidth
- NVIDIA - Best practices on GPU memory
- Micron - DDR5 datasheet and bandwidth specs
- JEDEC - Official DRAM interface standards
TOP QUESTIONS
How is Memory Bandwidth calculated?
It approximates as bus width × transfers per cycle × frequency × channels. Effective bandwidth depends on access patterns and overheads.
Category: Example
What limits Memory Bandwidth in practice?
Uncoalesced accesses, cache misses, contention, and interconnect bottlenecks like PCIe limit effective throughput.
Category: Risks
How does Memory Bandwidth differ from Memory Latency?
Bandwidth measures throughput rate; latency measures time to start a transfer. Both shape performance.
Category: Misunderstanding
Why is Memory Bandwidth crucial for ML?
Training often becomes bandwidth-bound when moving large tensors; sufficient bandwidth keeps compute units fed.
Category: Relevancy
How to improve Memory Bandwidth utilization?
Use contiguous accesses, batching, data locality, and faster memory technologies like HBM or multi-channel DDR.
Category: HowTo
What is a common mistake regarding Memory Bandwidth?
Optimizing compute without addressing memory bottlenecks leads to underutilized GPUs or CPUs.
Category: Mistakes
How do caches affect Memory Bandwidth?
Effective caching reduces external memory traffic, improving observed bandwidth and performance.
Category: Opinion
What metrics indicate bandwidth-bound workloads?
High memory throughput with low compute utilization suggests bandwidth-bound kernels.
Category: Example
What’s a hot topic around Memory Bandwidth?
Advances in HBM3 and chiplet architectures to scale bandwidth for AI accelerators.
Category: Topic