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What happens when a GPU reads memory | Doubleword

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Following an LDG.E SASS instruction through the hardware units in an RTX 4090.

Our previous post followed a vector-add kernel — c[i] = a[i] + b[i], one thread per float — from nvcc down to the warps. We went into a lot of detail on how the kernel was launched, but we also left a lot out. This time, we’re going to address our omissions, and follow the path the critical SASS instruction (a global load) takes through the hardware — in this case, since it’s under my desk, an RTX 4090We do this kind of reverse engineering for performance reasons, at least in principle (for a great rationale, see 'Why these details matter' in the Citadel microbenchmarking paper). For the…

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