look at this website Nvidia’s High-End Datacenter type GPU for server machines, the Tesla P100, doesn’t use all the 250 Pascal Cores on the build.
According to Nvidia, the P100 card uses 56 out of the 60 SM units available on the Pascal GP100 architecture.
However ,there is is no clear word from Nvidia about why the card uses less cores, but it could possibly due to performance issues. A 610mm square die makes up the Pascal GP100, which is the largest ever seen from the manufacturer.
The Pascal GP100 is the most complex GPU ever built, using the TSMC 16nm FinFET processing node and the first to use HBM 2.0 memory and is also one of the most powerful GPUs ever built featuring 3584 CUDA cores and a BCLK of 1328Mhz, which boosts up to 1480Mhz.