Vengeance DDR3 RAM not working at its rated top speed.

I cant get my 16Gb of RAM to work at their rated speed.

Motherboard: Gigabyte GA-P55M-UD2, Rev 1.0, Bios F11
CPU: Intel i5
2x Corsair Vengeance DDR3 4GB DIMM rated at 2133MhZ , CMZ8GX3M2A2133C11B, 11-11-11-27, 1.5v
2x Corsair Vengeance DDR3 4GB DIMM rated at 2133MhZ , CMZ8GX3M2A2133C11R, 11-11-11-27, 1.5v
The R and B signifying the colour of the heat sink.

I can mix them up and place any 2 of the DIMMS into the MoBo as a 8GB pair and run the memory at 2133MHz using the XMP, but if a put them all on the board (making 16GB) the fastest I can get hem to run is 1600MHz. If I use XMP in the setup, the PC fail sto boot and reboots with the RAM running at only 1333MHz.
The MoBo is rated for 16GB of DDR3 upto 2200MHz.

Sysoft Sandra confirms all four DIMMS are the same and quotes a series of timings that are identical for each DIMM.

If tried various Bios changes with no effect, including upping the DRAM voltage to 1.6v

Any got any ideas what might be wrong.


PS this is my first posting here - site was recommended by my son, who has unfortunately grown up, moved away and cant easily solve my PC problems for me anymore :-)
5 answers Last reply
More about vengeance ddr3 working rated speed
  1. With all 4 ram slots populated, it's not uncommon for the ram to run at a slower speed. I'd say there's nothing wrong with the board or ram. Not worth switching boards for; the new board may do the same.
  2. Thanks
    Is there nothing I can do to up the speed with all 4 DIMMS?
    If not, then I might as well go back to just 8GB running at 2133MHz instead of 16GB running at only 1600MHz :(
  3. I'd say you've done about everything you can; it's tough to get all four ram sticks running in sync when overclocking. Good luck.
  4. So the information supplied in the Gigabyte manual is deliberately misleading in that it says the MB supports 16GB and XMP memory, but fails to mention it can't do both at the same time. Rather disappointing to say the least. :(
  5. You need to raise the VCCIO and dimm voltage, especially for sandy bridge CPU's. anything older sandybridge isn't going to hit 2133. If you would post which CPU you are using it would be easier to help you out.
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