The PIN information is encrypted within Target’s systems and can only be decrypted when it is received by our external, independent payment processor. What this means is that the “key” necessary to decrypt that data has never existed within Target’s system and could not have been taken during this incident.

But what if the benchmark is larger than the memory size of the GPU? I don't know the actual size, but I guess they use at least realistic amounts of data (larger than the memory of the GPU card), so that would prove your theory wrong!