java applet slow on window 7 (64bit) machine

I am running java applet on windows 7 64bit (firefox 39.0). It take 10 second to load(showing java process icon meanwhile ) where as it take 1 second to run on window 8 64bit machine(firefox 39.0). it's also fine on 32(bit) window 7.

Why it is slow on window 7(64bit).

via Chebli Mohamed