RAM wont run at full speed after adding 2 more sticks

[Joshua Eve]

When I build my PC I originally had 2x4GB sticks of RAM running at 1866 MHz and they worked perfectly with no issues enabling XMP. After adding another 2 sticks of the same RAM I can no longer boot at 1866 MHz without getting a boot failure message. The only way to get the PC to boot is to run the ram at 1334 MHz but was wondering if there is anything I can do to get the RAM running at the original or faster speeds again.

CPU-Z Screenshots: http://imgur.com/a/2anCj

Rest of Specs: FX 6300 @ 4GHz
Gigabyte 970-A DS3P Rev 1.0 (Bios Version F2j)

 

[Barty1884]

Mixing & matching RAM can be a crapshoot. Replacing your 2x4GB with a 2x8GB kit would achieve the same end result with less hassle.

Do both sets of RAM actually support 1866MHz? If they do, their XMP profiles are likely a little different and need additional voltage etc.
If they don't (or if the XMP profiles differ), they will run at the common denominator which, for DDR3 is 1333MHz.

 

[Joshua Eve]

Mixing & matching RAM can be a crapshoot. Replacing your 2x4GB with a 2x8GB kit would achieve the same end result with less hassle.

Do both sets of RAM actually support 1866MHz? If they do, their XMP profiles are likely a little different and need additional voltage etc.
If they don't (or if the XMP profiles differ), they will run at the common denominator which, for DDR3 is 1333MHz.

All sticks of RAM are the same with the same part number so they should all be able to run at 1866 MHz.

 

[thx1138v2]

Some times sticks of RAM from the same batch won't run together due to process variation in manufacturing. That's why RAM is sold in "kits" - the sticks are tested together to ensure they will run together.

 

[Joshua Eve]

Some times sticks of RAM from the same batch won't run together due to process variation in manufacturing. That's why RAM is sold in "kits" - the sticks are tested together to ensure they will run together.

You learn something new everyday, Thank you!