Blackwell: Nvidia's GPU

Summary

Nvidia has a long tradition of building giant GPUs. Blackwell, their latest graphics architecture, continues that tradition. GB202 is the largest Blackwell die. It occupies a massive 750mm2 of area, and has 92.2 billion transistors. GB202 has 192 Streaming Multiprocessors (SMs), the closest equivalent to a CPU core on a GPU, and feeds them with a massive memory subsystem. Nvidia’s RTX PRO 6000 Blackwell features the largest GB202 configuration to date. It sits alongside the RTX 5090 in Nvidia’s lineup, which also uses GB202 but disables a few more SMs.A high level comparison shows the scale of Nvidia’s largest Blackwell products. AMD’s RDNA4 line tops out with the RX 9070 and RX 9070XT. The RX 9070 is slightly cut down, with four WGPs disabled out of 32. I’ll be using the RX 9070 to provide comparison data.A massive thanks to Will Killian for giving us access to his RTX PRO 6000 Blackwell system for us to test. And so, a massive thanks goes out to him for this article!GPUs use specialized hardware to launch threads across their cores, unlike CPUs that rely on software scheduling in the operating system. Hardware thread launch is well suited to the short and simple tasks that often characterize GPU workloads. Streaming Multiprocessors (SMs) are the basic building block of Nvidia GPUs, and are roughly analogous to a CPU core. SMs are grouped into Graphics Processing Clusters (GPCs), which contain a rasterizer and associated work distribution hardware.GB202 has a 1:16 SM to GPC ratio, compared to the 1:12 ratio found in Ada Lovelace’s largest AD102 die. That lets Nvidia cheaply increase SM count and thus compute throughput without needing more copies of GPC-level hardware. However, dispatches with short-duration waves may struggle to take advantage of Blackwell’s scale, as throughput becomes limited by how fast the GPC can allocate work to the SMs rather than how fast the SMs can finish them.AMD’s RDNA4 uses a 1:8 SE:WGP ratio, so one rasterizer feeds a set of eight WG...