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First-ever (and successful?) OC to 4.8, but w/cooling concerns

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FORDification

New Member
Joined
Oct 17, 2011
This is my first-ever overclocking attempt, and while I'm semi-happy with it overall, I'd like some input from those with more experience than me regarding 100% load cycle temps.

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BUILD SPECS:

Case: Rosewill Challenger
Intel Core i5-2500K 3.3 (w/4.8 OC)
Asus Sabertooth P67 (Rev. 3.0) - 1502 BIOS
PSU: Antec High Current Gamer Series HCG-900 900W (bottom intake, rear exhaust)
GPU: GeForce GTX 560Ti 1GB
Cooler Master Hyper 212+ (single 120mm push fan)
Corsair Vengeance DDR3 1600 (4 x 4GB)
Boot drive: Corsair M4 128GB SSD
Storage: 2 x Seagate Barracuda 7200.12 500GB SATA 6.0Gb/s; 2TB Western Digital Elements external USB
Win7 Home Premium 64-bit

Fans:
120mm front intake
120mm rear exhaust
120mm side intake
140mm top exhaust
120mm CPU cooler (push mode, aimed towards rear exhaust)
50mm motherboard assist

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I just built this new rig a week ago, and decided a couple days ago to try overclocking. Being a total newbie at this, I have very little understanding about such things. However, using the Asus UEFI and following a guide on another forum that was written by an Asus rep, I have my i5-2500K overclocked to 4.8 with the following specs:

Turbo Ratio: By Per Core (set to 48 on all four)
Internal PLL Overvoltage: Auto
Load-line Calibration: Ultra-High
VRM Fixed Frequency Mode: 350
Duty Control: T.Probe
CPU Voltage: Manual Mode @ 1.425

So...the rig runs well, and after giving it a full day doing light-duty stuff, I decided to hit it with Prime95 to see just how stable it would be. I ran it for almost two hours and got no errors, but the temperatures were a bit higher than I'd like to see, as reported by Real Temp. With idle temps about 38C and the ambient room temp about 75F, the workout with Prime95 was pushing the core temps into the mid-to-upper 70s, with a few seconds getting into the low-to-mid '80s...and a couple short spikes hitting 85C. It would only hit that 85C for a couple seconds, and then drop back down to the upper-70s. However, at 85C my motherboard flashed an on-screen warning at me, and even though the temps mostly leveled-off in the upper-70s, I decided to stop the test. Within 3-4 seconds the temps had returned to 38C.

Since the Hyper 212+ only had a single push fan, and I had several other new fans to use, I decided to try adding a second pull fan. The CoolerMaster fan that came with the Hyper 212+ has a 4-pin mobo header connector and a Molex connector for a 2-pin fan, so I hooked the second pull fan to the Molex connector, so that both fans were being powered by the same mobo header...and then fired things up again. However, the temps rose even faster than before and mostly leveled off in the low-80s, but again hitting the 85C mark pretty quickly, so I again shut it down. I removed the second pull fan and fired it up again...and found the temps didn't rise as quickly, but I was still bumping into the upper-70s and low-80s.

After thinking about it, I decided that maybe the cause of the slightly-higher temps with the second pull fan was because it was a different brand (Rosewill, that came with the case), and was possibly running at a slightly different RPM, essentially causing an airflow obstruction. So I'm thinking that I might have better luck running two identical CoolerMaster fans, running both 4-pin fans off the same mobo header with a splitter. (The Asus manual states this header can handle 1A (12W).) However, the reading I've done suggests that a second fan might only drop the temps a couple degrees at most, and probably isn't worth the trouble overall.

FYI: I did remove the cooler, cleaned it and the CPU up and checked for straightness, then reapplied the paste and reinstalled.Idle temps remained the same at about 38-39C.

Another thought I had was possibly dropping the Vcore voltage down a bit, thinking that less voltage would equal less heat. Am I thinking right? What voltage setting would you recommend I start with?

I know that with how I use my computer, I'll virtually never see a 100% duty cycle, even with some mild gaming that I might occasionally do, so I'd probably be OK, but if I decide to try bumping the OC up some more just to see what it's capable of, the cooling issues will need to be dealt with first. Then I can continue learning as I go. I'd definitely appreciate any input I can get.

Thanks!
 

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You may just be pushing a bit too hard on the 212+ for 1.425 with 100% load. The second fan really should have helped, I'm guessing (along with your guess) is that one was pushing/pulling too hard/soft for the other causing an issue which is possible.

I would start off a little lower, see what you can get to happen at around 1.35-1.4v and see the maximum speed you can get at those points while watching the temperatures, then slowly move up from there.
 
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