VRAM-residency challenge
The VRAM-residency challenge is a timed test of whether data is held in a GPU's on-board memory.
It comes from a 2026 study by Monfared and colleagues. The verifier first loads a large block of challenge data into GPU memory. At random times it sends fresh nonces, and the GPU must run a keyed, memory-hard hash over the stored block and return a digest.
If the block has been moved to host memory, each access crosses the PCIe link and the answer arrives late. On an H100 with 60 GB of challenge data, the gap between the two cases exceeded 350 ms. The test adds little power or throughput cost, but by design the challenge data occupies a large part of GPU memory.
The study covers a single GPU. It defines no thresholds and reports no error rates. The paper links no code.
A published experiment on an H100 separates data held in GPU memory from data held in host memory by more than 350 ms, on one GPU and without a detection threshold.
Assessed use: detecting whether verifier-supplied data remains in a single GPU's memory
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What it is
The VRAM-residency challenge is a test of whether data sits in a GPU's own memory, described by Monfared, Ganji, Tajik and Holcomb in a 2026 preprint 1. The paper uses VRAM and HBM, for high-bandwidth memory, to mean the GPU's on-board memory 1. The test is one application of timed challenge-response. The same paper's compute probes are covered in GPU contention probes.
How it works
- Load. Before measurement starts, a large block of incompressible challenge data is stored in GPU memory 1.
- Challenge. At random times the verifier sends fresh nonces 1.
- Compute. The GPU runs a keyed, memory-hard hash over the stored block. Each memory access depends on the result of the one before, so the work is bound by memory bandwidth and cannot be computed ahead of time 1.
- Answer. The GPU returns one digest. The verifier checks that it is correct and records the response time 1.
If the block has been moved out of GPU memory, each access has to cross the PCIe link from host memory, and the answer arrives late 1.