Why is my bus speed lowering when I use XMP profile on memory?

[Peddeh]

Hello, noob here. Completely new to this, so I haven't a clue what is up or what to do about it.

So I'm using a 4930K on the ASUS Rampage IV Formula motherboard, with latest BIOS. I have 16GB of RAM (2 (4x4GB) packs of these to be specific http://www.amazon.co.uk/gp/product/B00A771ZWI/ref=oh_details_o03_s00_i00?ie=UTF8&psc=1).

Problem is, whenever I set either of the XMP profiles in the BIOS, the Bus Speed is dropping from 100.00MHz to 98.98MHz. Now, this doesn't look like a big difference, but it's bugging me frown.gif

I'm suspecting I simply have incompatible RAM, and if this is the case what kit would you recommend for this board + CPU?

Many thanks!

 

[hunter315]

If your default bus speed is actually 100.00 you got the most ideal crystal ever shipped, normally there is variation in the bus speed, my M4A79T board has a bus speed of 200.7 MHz, variations are normal and you are talking about a 1.02% variation which isn't much.

Can you post CPU-z screenshots of before XMP and after XMP as well as what the base settings and the XMP settings are? Generally the bus speed is defined by the oscillator on the board and doesn't really care what else changes as it is well isolated, so if you do have dynamic fluctuations in yours this is intriguing.