Cuda out of memory despite I do have more memory

2.76b Gtx 970 (4g)
says mem:7xxM, peak:7xxM, cuda error: out of memory in culaunchkernel…

gpu wasn’t occupied by any but Cycles, what’s causing this?

ps. I have dual monitor, but I don’t reckon they eat that much of gpu memory?

ps. I have dual monitor, but I don’t reckon they eat that much of gpu memory?

It can, try to test this with GPU-Z.
Do you have this error with default cube?
I have a 4 GB card too but never got problems with cuda error.
Please add your system specs, was only guessing about your OS, Windows?

Cheers, mib