Bump map: different results CPU vs GPU

[bardo]

Hi,
I've seen a difference on rendering bump map from CPU to GPU.
CPU
uiV2Jqe.jpg

GPU
hiBN8Tg.jpg

Is it something expected or not?

Tested both viewport rendering and final rendering on VFB (GPU left, CPU right, noise is different to have a quick feedback but the bump map difference shouldn't be a noise issue)

X6BNX0D.jpg

Tested on nightly vray_adv_70010_blender420_x64_217