PTX

GPU Microarchitecture

CUDA Register Mapping: From PTX to SASS

Introduction Register allocation is one of the critical aspects of GPU programming. On CPUs, the hardware’s “out-of-order” execution engine hides inefficiencies through register renaming, dynamically managing hundreds of physical registers behind 16 visible ones(General Purpose Registers). GPUs work differently: the per-thread register footprint chosen by the compiler becomes a real occupancy resource, with no CPU-style dynamic register renaming safety net.

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GPU Microarchitecture

CUDA PTX: Learning to Read NVIDIA's Virtual ISA

TL;DR PTX is not the real hardware ISA. It is NVIDIA’s virtual instruction set that sits between CUDA C++ and SASS. PTX is the best layer for learning how the compiler thinks about types, addresses, predicates, and memory spaces. SASS is where architecture-specific details appear: actual opcodes, scheduling metadata, scoreboard behavior, and pipeline usage. If you can read PTX, you can usually answer: what computation is happening, what memory space it touches, and why the compiler generated a certain structure. If you want to optimize the last 20%, you eventually need to correlate PTX with SASS and measured hardware behavior. CPU Baseline: Why GPUs Need a Virtual ISA Layer On CPUs, most people think in terms of:

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