Why Nvidia’s Blackwell GPU Outshines AMD’s RDNA4 – A Deep Architectural Dive

Overview

Nvidia has long pursued massive GPUs, and its latest Blackwell architecture continues this trend. The flagship GB202 chip occupies 750 mm², contains 922 billion transistors, 192 streaming multiprocessors (SM), and a large memory subsystem. AMD’s RDNA4 series, exemplified by the RX 9070, serves as a performance benchmark.

Key Updates

CPU updates – evolution of Intel/AMD architectures and domestic CPU designs.

GPU updates – Nvidia’s transition from Fermi to Hopper (Blackwell) and AMD’s move from RDNA2 to RDNA4.

Memory and storage technology improvements.

Known issue fixes.

More than 40 pages of PPT documentation.

SM Front‑End

When work is assigned, each SM fetches shader instructions and delivers them to execution units. Blackwell uses fixed‑length 128‑bit (16‑byte) instructions and a two‑level instruction cache (four private L0 caches per SM and a shared L1 cache), inherited from the post‑Turing/Volta designs.

SM Memory Subsystem

Blackwell’s SM‑wide 128 KB storage block is split between L1 cache and shared memory. Unlike AMD, which keeps the L1/L2 split static, Nvidia can re‑allocate the entire block as L1 cache when kernels do not require local memory, giving flexibility but potentially higher L2 bandwidth demand.

Execution Units

Blackwell reorganises its FP32 and INT32 pipelines into a single 32‑bit wide execution pipeline, allowing simultaneous INT32 and FP32 operations without stalls. Each SM can issue 16 INT32 multiplies per cycle, four times the rate of Pascal or RDNA GPUs.

Atomics

GPU atomics are handled by dedicated ALUs close to the memory hierarchy. Nvidia provides 16 INT32 atomic ALUs per SM, while AMD offers 32 per WGP. This gives Nvidia an advantage in local‑memory atomic throughput.

GPU‑Wide Memory Subsystem

Blackwell retains a two‑level cache hierarchy but expands L2 capacity, achieving ~8.7 TB/s bandwidth, slightly higher than the RX 9070’s 8.4 TB/s. L2 latency is around 130 ns, positioned between Nvidia’s earlier designs and AMD’s Infinity Cache.

Performance Benchmarks

FluidX3D, a memory‑bandwidth‑intensive fluid simulation, demonstrates Nvidia’s RTX PRO 6000 (Blackwell) vastly outperforms AMD’s RX 9070 in both FP32 and FP16 modes, confirming the architectural advantages in real‑world workloads.

Power and Scaling

Blackwell’s 750 mm² die targets 575–600 W, pushing the limits of consumer‑grade PCs, while AMD’s RX 9070 caps at 220 W. The larger SM count and higher L1/shared memory capacity give Nvidia a decisive edge in high‑end markets.

Future Outlook

2025 will see intensified competition as Intel’s GPU efforts mature. In data‑center space, AMD’s MI300 shows strong performance, but in the high‑end consumer segment Nvidia’s Blackwell currently dominates, thanks to its massive core count, large L1/L2 caches, and superior memory bandwidth.