Impossible to get Prime95 Large FFTs stable?!

[andy5174]

System Spec
M/B: Gigabyte P55A-UD5

CPU: i5-750@3.60GHz(180x20), CPU-Z 100% load Vcore=1.20V

RAM: Kingston KHX1600C8D3K2/4GX CL8, 1600MHz, 2x2GB@CL8, 1440MHz(180x8), 1.58V

HDD: Seagate ST3500418AS 500GB, WD WD1001FALS 1TB

PSU: HX620

Stability test program: Prime95 x64 v25.9 & Memtest86+
Small FFTs test: stable for more than 24 hours

Memtest86+: 14 hours-12 minutes Standard test with 26 passes and 0 error

Large FFTs test: the best I can get for Large FFTs is 13 hours- 41 minutes; mostly I get less than 5 hours stability

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Does anyone get LARGE FFTs test of Prime95 x64 v25.9 stable for more than 14 hours on a 35%+ OCed i5, i7-8xx?

If so, could you tell me what the following settings are?

Load-Line Calibration(LLC) ON/OFF?
BIOS Vcore?
CPU-Z idle Vcore?
CPU-Z 100% load Vcore?
QPI/Vtt/IMC voltage?
PCH voltage?
CPU PLL voltage?

 

[jsc]

Large fft's show up problems with memory.

If small fft's (testing CPU) run without problem, your memory is probably your problem.