Will 1066 memory "underclock" to 800


Dec 23, 2011
I picked up an Intel Workstation Board S5520SC and have two E5645s CPUs inside. I also picked up two KVR1066D3Q8R7SK3/24G kits to bring the system up to 48GB of RAM. The system supports a wide array of memory configurations as outlined here: http://imct.intel.com/ListMemConfigs.aspx?pid=E5645&bid=S5520SC. At 1066 MT/s you can only use 48GB of Quad Rank memory, however at 800 MT/s you can double them up and get 96GB. I can use Dual Rank memory, however this is about as easy to find as a unicorn these days. Wintec has 24GB Dual Rank kits (3SH10667R5-24GT) but the only vendor that has them is NewEgg, they have one kit and after that they don't know if they will pick up more. The Quad Rank Kingston kits (KVR1066D3Q8R7SK3/24G) are pretty abundant, but I am reaching the end of my knowlege around this.

My question is whether 1066 Quad Rank memory will work in this configuration and simply underclock to 800 MT/s vs 1066 MT/s. I've seen others on the threads complain about this happening, but what if this is your desired configuration? Sounds strange, but for my purposes I simply need the memory capacity for virtualization testing. Thanks to anyone who can help expand my knowlege on this subject.
Most of the time the bios will allow you to select a memory speed.

The only time i had an issue with memory speed was on a Compaq laptop that had no such bios options and was unstable with the next speed(400 up from 333...see how old this is) up because it tried to run at that speed but could not deliver the needed voltage. The solution for me was just to flash the memory to a lower speed and all was well(just one stick since it follows the slowest stick).

Your best bet is to check the bios or even get a hold of Intel for confirmation.