Different result precision between different gpus with the same program

I have a problem with my program.I ran my program a few times on my GTX980 and i got the same results.But when program runs on P4, the accuracy of the results obtained from each run is not the same.All calculations in the program only dnn. The result like: output1:2.70637 -0.59397 -2.39845 -1.00066 -0.27046 output2:2.70637 -0.593971 -2.39845 -1.00066 -0.270459