I did miss it. And it is interesting. There are 6 regions which show this bad performance even while one of test had enough of free vram to accommodate any overhead caused by CUDA error. Interesting enough, In test where BF was running in background some bad regions were allocated before there was need to do so. And all bad regions had same performance in both tests 1x better than average, 3x average, 1 worse than average and 1 even worse than that. At this point I would say that this CUDA test is not defective and truly points towards some issue. If anyone has environment for compiling CUDA code, I will modify it to eat exactly 3GB of VRAM. And then victim should try to start in remaining (presumably bad) memory region some game even small which needs like 500MB of VRAM. Should prove for sure that there is something very bad.