Overclocking problem on kubuntu 14.10 x64 (nvidia gtx 750)

hello

I have a problem for overclock/downclock my gtx750 with nvidia-settings
I have installed version 340.65 of nvidia pilote on kubuntu 14.10 x64

I use the command line through nvidia settings
return of command are

~$ nvidia-settings -a [gpu:0]/GPUGraphicsClockOffset[2]=1 -a [gpu:0]/GPUMemoryTransferRateOffset[2]=1

ERROR: Error parsing assignment ‘[gpu:0]/GPUGraphicsClockOffset[2]=1’ (Unrecognized attribute name).

~$ nvidia-settings -a [gpu:0]/GPUGraphicsClockOffset[1]=-20 -a [gpu:0]/GPUMemoryTransferRateOffset[1]=1
ERROR: Error parsing assignment ‘[gpu:0]/GPUGraphicsClockOffset[1]=-20’ (Unrecognized attribute name).

This attribute work on my gtx570 and gtx550ti

what is the argument to use for nvidia 7XX serie ?

nobody ?

it is impossible to overclock a gtx 750 now?

Does it work via the nvidia-settings GUI?