Prime not supported with Nvidia GeForce 820M

[DUVAL Jean-Pierre]

uname -a
Linux CX61-2PC-1298 3.13.0-43-generic #72-Ubuntu SMP Mon Dec 8 19:35:06 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

sudo lshw -C display
  *-display NON-RÉCLAMÉ
       description: 3D controller
       produit: GF117M [GeForce 610M/710M/820M / GT 620M/625M/630M/720M]
       fabriquant: NVIDIA Corporation
       identifiant matériel: 0
       information bus: pci@0000:01:00.0
       version: a1
       bits: 64 bits
       horloge: 33MHz
       fonctionnalités: pm msi pciexpress bus_master cap_list
       configuration: latency=0
       ressources: mémoire:f6000000-f6ffffff mémoire:e0000000-efffffff mémoire:f0000000-f1ffffff portE/S:e000(taille=128) mémoire:f7000000-f707ffff
  *-display
       description: VGA compatible controller
       produit: 4th Gen Core Processor Integrated Graphics Controller
       fabriquant: Intel Corporation
       identifiant matériel: 2
       information bus: pci@0000:00:02.0
       version: 06
       bits: 64 bits
       horloge: 33MHz
       fonctionnalités: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       ressources: irq:48 mémoire:f7400000-f77fffff mémoire:d0000000-dfffffff portE/S:f000(taille=64)

nvidia-settings -v
version 346.22 (buildd@lgw01-10) Tue Dec 9 08:42:45 UTC 2014

nvidia-settings &
** Message: PRIME: No offloading required. Abort
** Message: PRIME: is it supported? no

The GUI is minimalist. There is no entry for Prime. Impossible to switch from Intel Haswell Mobile to Nvidia graphic card.

[cirelli fabrizio (cirelli94)]

The same append with GTX 850M

[Vasiliy (count0-3)]

Also have 820m Optimus technology, and can't get prime worked, just bumblebee, sometimes (1 of 10 ;)