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GPU memory bandwidth: how it is calculated, when it limits FPS and how caches change the picture

Memory bandwidth is how many gigabytes per second a GPU can move between its cores and VRAM: bus width in bytes × memory speed in Gbps (256-bit × 20 Gbps = 640 GB/s). High resolution, ray tracing and large textures are bandwidth-hungry, and when the cores wait for memory the frame rate drops — which modern GPUs offset with big on-die caches (AMD Infinity Cache, NVIDIA's 32–96 MB L2).

bandwidth · GB/s · effective bandwidth · Infinity Cache

📅 Updated 👥 FPSHQ Team · methodology

128-bit8 × 16 bit192-bit12 × 16 bit256-bit16 × 16 bit
Memory bus: more lanes — more bandwidth Bandwidth = bus width × effective clock

Key figures

From the FPSHQ database, as of Oct 14, 2026

67%of GPUs since 2020 have ≥ 12 GB
52tier S GPUs

The formula and typical values

Vendors quote "effective bandwidth" that adds cache hits; it is a marketing estimate, but the underlying idea is real: a cache hit rate of 50–70 % at 1080p halves memory traffic.

CardBusMemoryBandwidthLast-level cache
RTX 4060128-bitGDDR6 17 Gbps272 GB/s24 MB L2
RX 7600128-bitGDDR6 18 Gbps288 GB/s32 MB IC
RTX 4070 Super192-bitGDDR6X 21 Gbps504 GB/s48 MB L2
RX 9070 XT256-bitGDDR6 20 Gbps640 GB/s64 MB IC
RTX 5080256-bitGDDR7 30 Gbps960 GB/s64 MB L2
RTX 5090512-bitGDDR7 28 Gbps1792 GB/s96 MB L2

When bandwidth is the limit

Symptoms: a card that is competitive at 1080p loses more than the usual 35 % going to 1440p and more than 55–60 % going to 4K; memory overclocking yields noticeable gains; ray tracing and MSAA hit harder than expected. Cache hit rates fall as resolution rises because the working set (frame buffers, textures per frame) outgrows the cache, which is why 128-bit cards with 24–32 MB caches are 1080p products and 4K cards need 256-bit+ or GDDR7.

The FPSHQ measured dataset shows this scaling per card: the ratio of 4K to 1080p FPS for narrow-bus cards is consistently worse than for wide-bus cards of the same tier.

Improving effective bandwidth

CPU-side memory bandwidth (DDR4/DDR5) is a different topic — see RAM frequency and dual channel.

  • Memory overclock: +5–10 % clock → +3–8 % FPS in bandwidth-bound games
  • Lower resolution or use DLSS/FSR — bandwidth demand scales with internal resolution
  • Texture compression and smaller texture settings reduce traffic
  • Avoid MSAA and full-resolution SSR/volumetrics in bandwidth-limited cards
FPSHQ

On your PC

Enter your GPU (and CPU) — we calculate the effect of "Memory bandwidth" with the unified FPSHQ model using Cyberpunk 2077 as the example.

Save your PC in the account · Detect hardware with the app · Unified FPSHQ model estimate, not a measurement.

Where to use this on FPSHQ

GPU catalogCompare GPUsFPS calculatorBottleneckCan I run itGPU tier list

Forum discussions

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In short

What is Memory bandwidth?

Memory bandwidth is how many gigabytes per second a GPU can move between its cores and VRAM: bus width in bytes × memory speed in Gbps (256-bit × 20 Gbps = 640 GB/s). High resolution, ray tracing and large textures are bandwidth-hungry, and when the cores wait for memory the frame rate drops — which modern GPUs offset with big on-die caches (AMD Infinity Cache, NVIDIA's 32–96 MB L2).

of GPUs since 2020 have ≥ 12 GB
67%
tier S GPUs
52
updated · source: TechPowerUp GPU database, AMD Infinity Cache, FPSHQ model estimate

FAQ

How do I calculate GPU memory bandwidth?
Bus width ÷ 8 × speed in Gbps: 192-bit ÷ 8 = 24 bytes × 21 Gbps = 504 GB/s.
Is bandwidth more important than VRAM size?
They limit different things: size prevents stutter when full, bandwidth governs FPS at high resolution. Both matter for 4K.
What is Infinity Cache?
AMD's large on-die last-level cache (RDNA 2+) that serves memory requests without going to VRAM, boosting effective bandwidth.
Does memory overclocking help?
In bandwidth-bound scenarios (4K, RT) by a few percent; otherwise little.

Sources

FPSHQ Team · methodology · methodology · Updated

✏️ Found a mistake? Suggest an edit

Edits are moderated. Say what to fix and, if you can, add a source (NVIDIA/AMD/Intel docs, the game developer).

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