I5 1.275 at stock clocks?

[LowRes]

This is problem: (133x20 + turbo) Prime95 stable with Vcc 1.25 (BIOS) 1.212 (CPUZ) but in CPU intensive games or at low resolutions and graphics settings I have stuttering and momentary freezes (GPU intensive games such as Crysis and the unigine benchmark are completely smooth), increasing Vcc in BIOS to 1.275 (1.248 CPUZ) fixed this, however it seems too high to me. Coretemp shows totally acceptable load temps (65, 24Amb) with stock cooling. As a side note i can up the Bclk to 172 and have a P95 stable system with the same Vcore (ram at 1032), no stuttering, 5C temp increase, turbo disabled.

Could it be due to the graphics card (5870) requirements and/or something to do with the i5 having PCIe controllers on the chip, or do i have a problem?

Stock cooling, memory at 1333 1.5, Turbo enabled, C1E disbaled, other C states enabled (tried with and without these). Btw Auto Vcc in BIOS had the voltage at 1.348 (CPUZ) on a single core (turbo'd).

Any ideas are much appreiciated. Trying to understand why my i5 needs so much more voltage than those tested in every article i read on the subject. Thanks

 

[LowRes]

EDIT: After a little playing around with this at lunchtime today I was watching CPUZ while the game is running - processor is switching multipiers all the time in turbo mode - 24, 21, 23, 22, 20 etc. When turbo is disabled and i manaully clock to 3.0 the freezing problem goes away (at Vcc 1.25), why would that be?

This is annoying - i'd like to make use of the turbo mode.

 

[LowRes]

Another update for anyone interested. Turns out the stock cooling isn't so good (big surprise). Using a Cooler Master 212 plus, everything is as it should be. Bios Vcc 1.23 (1.201 CPUZ) P95 (12hrs) and intel burn test stable, max 45C (21amb). All games are perfect. The whole system is more stable with better cooling, everything improved from the graphics scores to the performance of a wireless pci card. The freezing problem turned out to be a result of that particluar game not requiring much CPU power, the multiplier was dropping down to 9 intermitently. With better cooling the system doesn't seem to jump around between different Vcore and multipliers to the same extent. Maybe i just had a bad stock cooler or bad installation - was a pain to remove, a couple of pins jammed.