Freezing PC. Furmark CPU burn crashes, Prime95 not

[assembled]

Hello, I have the following PC build:
MB Asus M5A99FX PRO R2.0
CPU AMD FX-Series FX-6300 SAM3+ BOX FD6300WMHKBOX
RAM 2x Crucial Ballistix 4GB DDR3 PC3-12800 CL8 BLT4G3D1608DT1TX0
GPU Asus AMD/?ATI Radeon HD7790 1GB GDDR5 PCIE HD7790-DC2OC-1GD5
Case Nexus Tower Thrio 310
2x Nexus Case Fan 120mm D12SL-12 BLACK/?WHITE
HDD Western Digital CAVIAR Blue 1TB SATA 7200RPM 64MB WD10EZEX
LCD Philips 227E4QHAD
PSU Corsair CX600 ATX2.3 80+ 600W
Lite-On DVDRW 24X SATA Black IHAS124-04



During gaming (always) and sometimes during random activities PC freezes with looping sound and without any log entries, BSOD or any other information. I have:
ran multiple stress tests
tested RAM with memtest
tested HDD with mhdd and other tools
tried using only one or the other ram stick, booting from another drive with this result.
Tried disabling all audio devices.
Tried using windows 7 or windows 8 (problem is version independent).
Replugged every PC component from GPU to CPU.
Messed with BIOS settings from defaults to high performance. From OC to under-clock.
Tried various GPU drivers from the ones in CD to current or beta.

Temperatures are OK under any load.

Eventually I returned the PC without mentioned HDD to customer service. They can not find anything wrong with it either so back to start. I am quite desperate.

Anything else I could try besides selling the damn box?

 

[badboyrog2]

ok ...try to clear the cmos ...remove the cmos battery 30 sec and reinstal it
check which version of bios you have
check here
http://www.asus.com/us/Motherboards/M5A99FX_PRO_R20/HelpDesk_Download/

you can not see the real temps with fx cpu only margin temps...so still possible your cpu do overheating
check thermal paste and cpu cooler installation

remove completely the gpu driver and all assiociated files cleanly
reinstal the latest driver ( gpu )

go in the bios and set all to the default

let me know

how many ram you have..2X4gb or 2X2gb?
check in the bios if all voltages and temps are normal..
maybe your psu is tired ?
can you try with an other psu?

 

[assembled]

Thank you for your feedback. I now have stock BIOS settings, latest firmware, latest GPU drivers.

Finally I managed to get something repeatable. It takes 10s to 1 min. to hang the PC with Furmark CPU burner. Even though temperature stays under 50 C. Can it be some local hot spots? If I run 5 threads, it takes longer to hang.

I have stock cooler. Initially it had some silver thermal grease which I replaced with some white one laying around. Same result in both cases.

 

[assembled]

I am now running AMD Overdrive auto-tune and it is not crashing... Can there be a problem with automatically adjusted Vcore being adjusted too low? Overdrive keeps it ant 1,45 V and when using mentioned stress test is drops below that (will check it later).

Edit1: I tried fixing CPU voltage to 1.4 V. It does not help. It does not matter whether CPU frequency is 2,5 GHz or 4,3 GHz.
Using prime I can heat CPU to 68C without hanging, but FURMARK CPU burner hangs PC in seconds.

Edit2: Now running Furmark GPU test (GPU at 61C) and prime95 simultaneously for 10 minutes. I doubt it is a thermal problem as I can heat CPU to mentioned 68C without a problem. Nor it is a power problem: all voltages remain fixed under load. Vcore now is set to 1.40V.

 

[assembled]

Update: Real Bench stress test also hangs under fixed 1.40 V Vcore as well with default bios settings (automatic Vcore). I suppose, it is safe to say that there is an issue with MB or CPU?

 

[sHoRtBuSseR]

Not sure if you've fixed it yet, but the stock voltage for that chip from AMD should be 1.35 volts. What are you cooling the chip with? I am in the middle of getting 5GHz on my 8150. I might be of some help. I'm at 4.8 right now, but I am also pushing 1.52 volts... Also, don't use ANYTHING that says it will "auto clock" or "auto voltage" for you. I have never been able to use one of those things and NOT get a PC lock up. Just use your BIOS to change it. If you're on a good cooler, you should be able to go up to 1.45 volts without heating issues. 1.45 should be enough for 4.4 GHz on those chips.