Cycles works slower when using CPU with integrated gpu


My question might be dumb, but I’m just curious.
I remember that when I had my dedicated GPU and I was forced to switch to CPU (like to use SSS shader and later compose it to the rest of render), I remember it was rendering with decent speed (at least as for CPU).
Now I’m stuck for few days without any dedicated GPU so (obiviously) I use integrated one. But the strange thing is: When I want to render something it takes 3 or 4 times longer to start render and at least 2 times longer to render 20 samples.
Why is that? It’s like this GPU is integrated into CPU so CPU has less power to give for rendering…
I have AMD Phenom II x4 945 (but I doubt it matters anyway).

Why it renders slower?

Problem was in Spatial Split (or however it calls…). I’d close this thread if knew how. :expressionless: