Unstable i5 2500k system at base clock (reboots)

Hi all,

This is the first machine I build and I am in dire need of assistance.
My computer became unstable after I tried overclocking it to 4.0GHz following this guide: http://www.clunk.org.uk/forums/overclocking/39184-p67-sandy-bridge-overclocking-guide-beginners.html
So I reset the mobo CMOS using the jumper function to guarantee all setting would come back to default. The problem is that the computer kept unstable even after setting it to base clock. I ran tests and play games (to test) and I'll get system reboots when the system is under stress. Here's the list of what I did so far:
- The system reboots when I'm testing Large FFTs on Prime95 after not even 2 minutes.
- I ran Small FFTs for more than 2 hours on Prime 95 and it remained stable. I even ran it along with OCCT for some time just to push it even further and it didn't reboot.
- Also ran IntelBurnTest on high and it passed the 5 tests.
- FurMark Burntest for around 1 hour - GPU reached 79 celcius max (75 avg.)
- I ran memtest overnight and it passed 5 times. Factory defaults 9-9-9-27-1 (1.65v). I just changed the last number to 2 since a friend recommended.
- Play Witcher 2 and DiRT 3 - the system will reboot itself after playing from 15 to 45 minutes. Also, I noticed that on DiRT3 the game sometimes gets "jumpy" (like 2 FPS) for a few seconds. I also saw some pink artifacts when crashing on walls with the car when my pc was still overclocked.

Note that I probably did not fry anything since CPU Vcore was never set above 1.3v when overclocked to 4.0GHz. Also, 1.70v was the highest I went with memory.

This is my system spec:

- COOLER MASTER Hyper 212 Plus- http://www.newegg.com/Product/Product.aspx?Item=N82E16835103065

- Western Digital Caviar Black WD1002FAEX 1TB 7200 RPM 64MB Cache SATA 6.0Gb/s- http://www.newegg.com/Product/Product.aspx?Item=N82E16822136533

- Kingston HyperX 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) - http://www.newegg.com/Product/Product.aspx?Item=N82E16820104173

- Intel Core i5-2500K Sandy Bridge 3.3GHz (3.7GHz Turbo Boost) 4 x 256KB L2 Cache 6MB - http://www.newegg.com/Product/Product.aspx?Item=N82E16819115072

- Antec EarthWatts EA750 750W Continuous Power ATX12V version 2.3 SLI Certified CrossFire Ready 80 PLUS Certified Active PFC "compatible with Core i7/Core i5" Power Supply - http://www.newegg.com/Product/Product.aspx?Item=N82E16817371026

- SAPPHIRE 100312-3SR Radeon HD 6950 Dirt3 Edition 2GB 256-bit GDDR5 PCI Express 2.1 - http://www.newegg.com/Product/Product.aspx?Item=N82E16814102945

- ASUS P8P67 PRO - http://www.newegg.com/Product/Product.aspx?Item=N82E16813131771

- COOLER MASTER HAF 912 - http://www.newegg.com/Product/Product.aspx?Item=N82E16811119233

Any ideas of what's going on?

If someone could please help me out it would be great!

thanks in advance :)
3 answers Last reply
More about unstable 2500k system base clock reboots
  1. update:
    ok, so i changed the memory voltage to 1.5 and I could run a large FFT test for almost 24 hours. Sweet. I think I might have figured the issue. going to run more tests and post results.
    any ideas/suggestions?
  2. ok so after playing Dirt3 for half hour, I still notice "jumpy" frames and some pink artifacts tears on the screen sometimes when my car crashes or hit a tree. The computer did not reboot during the time I was playing, but again, it was just for 30 minutes.
  3. I have a similar system with and I 5 core processor exactly like yours. I am also seeing things like you see. What was your solution?
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