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Prime95 Rounding Error

Tags:
  • Memory
  • Intel i7
  • Overclocking
Last response: in Overclocking
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January 20, 2011 4:15:18 PM


I have an overclocked i7 920 with 6GB of RAM, everything has been fine for 8 months but added another 6GB of memory (total of 12GB) and I'm getting an error from Prime95 (FATAL ERROR: Rounding ..) but I've run memtest86+ for 18 hours (twice) with zero errors. But Prime95 will get errors within 5 mins. The memory is identical (make, model, etc) as the first set.

Any ideas?

Memory Specs:
Corsair TR3X6G1600C8 G
•Series: XMS3
•Model: TR3X6G1600C8
•Type: 240-Pin DDR3 SDRAM
•Capacity: 6GB (3 x 2GB)
•Speed: DDR3 1600 (PC3 12800)
•Cas Latency: 8
•Timing: 8-8-8-24
•Voltage: 1.65V

More about : prime95 rounding error

January 20, 2011 4:32:47 PM

Possible I guess ... I didn't get aggressive only sent to 3.8 GHz. I'll recheck w/ 6GB tonight but what would normally cause the rounding error when adding RAM. I would assume bad memory but MemTest86+ isn't giving any errors.

MORE OC details:

My stable 3.8Ghz settings are below:

Advanced CPU Features:
CPU Clock Ratio ................................ [19 ]
Intel(R) Turbo Boost Tech ................. [Disable]
CPU Cores Enabled .......................... [All]
CPU Multi Threading ..........................[Enable]
CPU Enhanced Halt (C1E) ................. [Disable]
C3/C6/C7 State Support ................... [Disable]
CPU Thermal Monitor ........................ [Enable]
CPU EIST Function ............................ [Disable]
Virtualization Technology ................. [Disable]
Bi-Directional PROCHOT .................... [Enable]

Uncore & QPI Features:
QPI Link Speed ..............................[x36] 7.2GHz
Uncore Frequency ..........................[x17] 3400MHz
Isonchronous Frequency ...............[Enable]

Standard Clock Control:
Base Clock (BCLK) Control .................. [Enable]
BCLK Frequency (MHz) .........................[200]
PCI Express Frequency (MHz) ............. [100]
C.I.A.2.................................................. [-]

Advanced Clock Control:
CPU Clock Drive ..............................[800]
PCI Express Clock Drive ................ [900]
CPU Clock Skew ............................ [0]
IOH Clock Skew ............................. [0]

Advanced DRAM Features:
Performance Enhance .......................... [Standard]
Extreme Memory Profile (X.M.P) ........... [Disable]
System Memory Multiplier (SPD) ........... [ 8]
DRAM Timing Selectable (SPD) ............. [Quick]

Channel A + B + C

Channel A Timing Settings:
##Channel A Standard Timing Control##
CAS Latency Time ..................[8]
tRCD ......................................[8]
tRP ........................................[8]
tRAS ......................................[24]
CR..........................................[2]
B2B........................................[-]


Advanced Voltage Control:
CPU Intel Core i7 920 D0 Stepping
Load Line Calibration .................... [Standard]
CPU Vcore ......................................[1.275]
QPI/VTT Voltage 1.150v .................[1.295]
CPU PLL 1.800v ..............................[1.80]
PCIE 1.500v ...................................[AUTO]
QPI PLL 1.100v ..............................[AUTO]
IOH Core 1.100v ............................[AUTO]
ICH I/O 1.500v ...............................[AUTO]
ICH Core 1.1v ................................[AUTO]

DRAM
DRAM Voltage 1.500v .............. [1.64]
DRAM Termination 0.750v.......... [AUTO]
Ch-A Data VRef. 0.750v ...........[AUTO]
Ch-B Data VRef. 0.750v ...........[AUTO]
Ch-C Data VRef. 0.750v ...........[AUTO]
Ch-A Address VRef. 0.750v ........[AUTO]
Ch-B Address VRef. 0.750v ........[AUTO]
Ch-C Address VRef. 0.750v ........[AUTO]


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a b K Overclocking
January 20, 2011 4:52:52 PM

Prime95 stresses the CPU more than memory, while Memtest stresses the memory more than the CPU.

With all six slots occupied, you may need to increase the DRAM voltage a bit. Or if you don't want to do that, try the RAM timings at 9-9-9-24. Some CPUs need timings loosened when all RAM slots are occupied.
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January 20, 2011 5:12:51 PM

Leaps-from-Shadows said:
Prime95 stresses the CPU more than memory, while Memtest stresses the memory more than the CPU.

With all six slots occupied, you may need to increase the DRAM voltage a bit. Or if you don't want to do that, try the RAM timings at 9-9-9-24. Some CPUs need timings loosened when all RAM slots are occupied.


How much would be typical? Right now its 1.64 ... would 1.66 be enough?

Thanks for the input!!
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January 21, 2011 7:21:09 PM

Leaps-from-Shadows said:
Prime95 stresses the CPU more than memory, while Memtest stresses the memory more than the CPU.

With all six slots occupied, you may need to increase the DRAM voltage a bit. Or if you don't want to do that, try the RAM timings at 9-9-9-24. Some CPUs need timings loosened when all RAM slots are occupied.



Bumped the DRAM Voltage from 1.64 to 1.66 and the Rounding Error has stopped.

But the machines seems to reboot under Prime95 after about 5-6 hours (at least my first test). Any additional pointers to get the system stable again after adding memory.

Thanks
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a b K Overclocking
January 21, 2011 7:29:20 PM

If it is rebooting try monitoring the temps. Did any program try and reboot windows itself (ie: windows update)
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a b } Memory
a b K Overclocking
January 22, 2011 12:16:26 AM

Before you go any further with the voltage, wasn't there some sort of limit on DRAM voltage for Intel chips? IIRC it was 1.65v -- higher than that and you could fry the chip.

I'd actually try loosening the timings before going any higher on the voltage.
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