CPU overclocking stopped giving increase in performance

[plapito]

So i have been over clocking MY I7-920 for almost 6 months now, and evreything was working great, i saw an increase in fps, my benchmarks were higher all around like 150+ on cinebench,. Now all of a sudden my benchmarks and everything has reverted back to when it was running stock bassicaly.. tested bench marks again and now im getting +2 on cinebench. bios did not revert back, still on 3.4ghz in bios, and also in cpuz. temps are not great but not to bad normally, 78C max full load or so. just cleaned out my pc today thinking maybe that could be effecting it but i am still getting the same results. not sure if maybe my cpu is just dying since its old and been used a lot but if anyone knows what could be causing this any input would be greatly appreciated as i am rather new to overclocking.

Thanks for your time.

My full list of hardware
Operating System
Windows 10 Pro 64-bit
CPU
Intel Core i7 920 @ 2.67GHz 58 °C
Bloomfield 45nm Technology
RAM
12.0GB Triple-Channel DDR3 @ 662MHz (9-9-9-24)
Motherboard
EVGA 141-BL-E757 (Socket 423) 26 °C
Graphics
2460G4 (1920x1080@144Hz)
SAMSUNG (1360x768@60Hz)
4095MB NVIDIA GeForce GTX 960 (MSI) 56 °C
Storage
465GB Seagate ST3500820AS ATA Device (SATA) 29 °C
223GB KINGSTON SA400S37240G ATA Device (SSD) 29 °C

 

[alceryes]

Download and run OpenHardwareMonitor in the background. Select log results. http://openhardwaremonitor.org/downloads/
Run your benchmarks.
See if your bus or CPU are downclocking during benches.