Just found this on newegg:
Other Thoughts: Most people don't understand that all RAM has boot speed, latencies and voltage programmed into the SPD of the DIMM that is read when you boot up your PC. All of the RAM makers use a safe boot frequency which is currently 1333/1600 MHz. for DDR3 RAM.
If your RAM also has an 1866 MHz. XMP rating which in the case of RAM like this G.Skill model , then 1866 MHz. can be selected by your BIOS when you boot, if the BIOS has this feature.
If the BIOS doesn't know to use the XMP setting, then you will need to go into the BIOS and manually set the frequency to 1866 MHz. Failure of your mobo to set the RAM frequency to 1866 MHz. on boot is NOT a defect or issue with the RAM. The BIOS reads what is programmed into the SPD for a safe boot frequency that will allow virtually any PC to boot without issues.
The 1866 MHz. or higher frequency is what the RAM has been tested to run at reliably. It does not mean that all PCs can run the RAM at that frequency.
As an example Deneb CPUs will typically only run RAM at about 1600 MHz. without isses. Thuban CPUs will typically run DDR3 RAM to 1800 MHz. and some times to 2000 MHz. depending on your CPU/IMC, mobo and RAM used. FX processors will run RAM at speeds in excess of 2000 MHz. - if the RAM is certified to run above 2000 MHz.
It's worth noting that extensive PC testing on both Intel and AMD desktop systems only showed a 1-2% increase in system performance going from 1600 MHz. to 2000 MHz. so don't expect big gains just by using higher frequency RAM because DDR3 RAM @ 1333 MHz. is not a system bottleneck, so there are minimal system gains to be had with faster RAM.
Manufacturer Response:
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Dear Customer
Thank you for such a great detail review. The current JEDEC standard is DDR3-1333 CL9 and DDR3-1600 CL11, so this is the maximum value any motherboard can automatically default to without enabling the performance profile. This allows the memory to work at a lower frequency even if the CPU or motherboard may not fully support a higher DRAM frequency. It is up to the user to manually input settings in BIOS, or enable the XMP (Intel) or DOCP/EOCP (AMD) enhanced performance profiles.
CPUs are designed to use standard RAM such as DDR3-1600, so any higher DRAM frequency will be limited by the CPU. To unleash the full potential of the system and maximize throughput, it is necessary to overclock the CPU frequency and Northbridge frequency. Once you do that, the higher DRAM frequency will make a significant difference to your overall system performance. There is a drastic gain to be had with faster RAM if configured properly. For example, a video that usually takes 15 minutes to edit with DDR3-1600 memory, can be reduced to 5 minutes with DDR3-2400 RAM and an overclocked CPU. The higher DRAM, CPU, NB frequency is extremely beneficial to those that deal with large files and need maximum bandwidth. For any further questions or concerns, please feel free to contact us directly.
Thank you
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