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Dominator GT ram 2000mhz to run at 1866. Stuck at 1600mhz

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November 6, 2012 5:35:18 AM

I just bought some 2000mhz Dominator GT ram and installed it. Its only running at 1600mhz and the multiplier is at the highest setting. I'm familiar with bios and can over clock a CPU, and can change ram timings. However i cannot get my ram to run at 1866mhz which is the max my MOBO (ga-880ga-ud3h) supports. My question is how do i do it. I've done my reading and have yet to find anything helpfull.
a c 186 à CPUs
a b } Memory
November 6, 2012 6:30:22 AM

Well, it really doesn't matter. 1333mhz and anything above won't do anything for performance....
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a b à CPUs
a c 347 } Memory
November 6, 2012 11:09:17 AM

Well a couple of issues, first it depends on your 'CPU' and second your MOBO 'revision, GA-880GA-UD3H maximum is listed between 1866MHz (OC) for 2.0, and 2000MHz (OC) in version 2.1 and above.

Assuming the Memory Clock limit is x8 then to acheve the higher RAM frequency you must increase the CPU Host Clock Control (FSB). Examples:
DRAM Frequency = Memory Clock * CPU Host Clock Control
1600MHz = 8 * 200MHz
2000MHz = 8 * X_MHz ; 2000MHz / 8 = 250MHz = CPU Host Clock Control
1866MHz = 8 * X_MHz ; 1866MHz / 8 = 234MHz = CPU Host Clock Control

'BUT' that also OC's the CPU, example Phenom II X6 1100T = 3300MHz / 200MHz (16.5)
CPU Frequency = CPU Clock Ratio * CPU Host Clock Control
note: 'CPU Clock Ratio' varies from CPU to CPU
CPU Frequency = 16.5 * 250MHz = 4125MHz vs 3300MHz
3300MHz = X_CPU Clock Ratio * 250HMz ; 3300MHz/250MHz = 13.2 = CPU Clock Ratio ; rounding
3300MHz = X_CPU Clock Ratio * 234HMz ; 3300MHz/234MHz = 14.1 = CPU Clock Ratio ; rounding
CPU Frequency = 13 * 250MHz = 3250MHz or slight under-clock or you can up the 'CPU Clock Ratio' to the next setting for a slight OC.
CPU Frequency = 14 * 234MHz = 3276MHz or slight under-clock or you can up the 'CPU Clock Ratio' to the next setting for a slight OC.

Now where Memory Frequency really impacts performance in with APU and iGPU performance, but if you have a discrete GPU then the performance differences will be very small and the OC required often does generate additional heat.

Depending on your CPU this information may offer additional information; see - http://www.gskill.us/forum/showthread.php?t=7688

Q - What CPU?
Q - What GPU?
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November 6, 2012 5:42:04 PM

CPU: AMD 955 BE (oc) to 4.0ghz
GPU: XFX Radeon 6970
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a b à CPUs
a c 347 } Memory
November 7, 2012 1:24:24 AM

alexxxmackie said:
CPU: AMD 955 BE (oc) to 4.0ghz
GPU: XFX Radeon 6970

Frankly, with anything less than a 6-core Phenom I wouldn't advise >DDR3-1600.
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