Motherboard Name: ASRock Z68 Pro3-M

Motherboard Chipset: Intel Cougar Point Z68, Intel Sandy Bridge

CPU Type: QuadCore Intel Core i5-2500K

Kingston Hyper X: 8 GB DDR3-1333 DDR3 SDRAM CL9

I'm trying to overclock it at 4.0 ghz, I got the stock cooler. My problem is that when i set the cpu ratio to 40(stock is 33) when it boot to the desktop i open cpu-z and its 4.0 ghz like i want it to be.After running prime95 for 2 minutes it multiplier goes down to 38 ,39,37  i want it to be stable like i chose in the bios(at 40) or is it normal  that it underclock the multiplier?

OK I had tried everything from disabling turbo boost, intel speedstep tech,fixed mode, offset mode,cpu load-line calibration,level 5,4,3,2,1 nothing works. fan speed are at max, cpu c3 state, cpu c6 state, c1E  disabled and enabled didn't work.

What are your temps, it could be that you're not supplying enough voltage to the CPU or that the CPU is getting a bit too hot (henceforth the clock going down.).

If it's not the temps, you could try messing around with the memory timings. I mean with some small changes it's possible you might get better results (such as the multiplier taking a longer time to work) but I haven't overclocked in a while so my knowledge of this subject is fuzzy. Still, it's worth a try. Memory tweaking is still essential to many overclocks high and low.

Hope we're able to help you out with your problem.

Its my friends i5 2500k, im trying to overclock which i recommended him to buy.He asked me "hey can you overclock it like yours" i said ok once i went to the bios its a total different one with a lot of new features. Max temps for his i5 2500k is 72, when running prime i was hitting max 64 so its not the temperature, i used high voltages so i could later lower it(so discard more voltages and high temperatures).

I had not touch memory timings yet i want to have a stable cpu overclock first. everything about memory is in auto even its is running at stock speeds.. I'm only using the cpu's multiplier so there is no reason to tweak memory's timing

Overclocking now is not what it used to be to the traditional way. I have an athlon ll x4 630 overclocked by me to 3.15 ghz using stock cooler max temps are at 68 (stock was 2.8) 

let me know if im correct or not :)

Thanks you for your opinion :)

I had not touch memory timings yet i want to have a stable cpu overclock first. everything about memory is in auto even its is running at stock speeds.. I'm only using the cpu's multiplier so there is no reason to tweak memory's timing

Auto is a bad thing when it comes to overclocking; mainly because there can't be one setting for one CPU. Every CPU is processed different, even though the architecture is the same on every CPU; therefore every CPU requires different ways of tackling it. CPU's could require less power or more power or they could require different parameters, it's all different.

I'm not a pro with 2500K overclocking but the stuff is mostly the same, I don't think there would be anything different then if you were overclocking with a i7-870 CPU (except for the lock multiplier.) You have to mess with some settings, try to figure out which one is best for the CPU; like a game of chess. Overclocking takes time, don't rush it.

I have to agree with you on that one. Auto is just not the right thing to do when overclocking, and more with RAMs.Yesterday before posting this, I noticed that the motherboard was giving more voltages to the ram than the spec for the ram but i didn't even look at the actual ram timing, i will take a look at that and set it to the manufacturers stock(manual way). Again i think that memory won't be responsible for a cpu multiplier drop but i will try that.

I think i found the answer once the core temp hits 81  it lowers the multiplier. max i can go is 3.898 the multiplier doesn't underclock itself

I am sure you thought of this, but I would never overclock a 2500k on a stock cooler.  Your CPU will start throttling at 80 and above, so along with a setting here and there in the BIOS you are just asking for instability.