SOLVED Which RAM speed will effectively work?

My question might be a little newbish but it has been years since I built my own system or gave any thought to the usual head scratching in regards to bottlenecks, system limitations, actual vs. claimed specs, etc.
I have a ASRock Extreme 4 Gen 3 P67 mobo and the specs say it can handle everywhere from 1033 to 2100 RAM speed. I want to go with either 1600 or 1866 but on the spec sheet the 1866 has in parentheses O.C. "1866 (O.C.)"
The 1600 does not. I have figured out the O.C. means overclocking.
What does the overclocking refer to? Can I purchase 1866 speed RAM and have it run at 1866 without overclocking or does it default to 1600 and then you have to overclock it to 1866? May sound a little silly but I know the P67 already is older technology and I would rather not pay more for faster RAM that without tweaking (that I might or might not indulge in) will not run at full speed.
Any help would be appreciated.

Overclocking refers to changing the memory multiplier. You hit it on the head. It will default to 1600Mhz and you change the memory multi to get to 1866.

That said, grab some 1600Mhz ram as ram is not the bottleneck even at that speed.

EarthDog said:

Overclocking refers to changing the memory multiplier. You hit it on the head. It will default to 1600Mhz and you change the memory multi to get to 1866.

That said, grab some 1600Mhz ram as ram is not the bottleneck even at that speed.

Click to expand...

Ok so the spec has to say 1866/1600 without the OC to mean it truly accepts said speed.
Gotch ya.
Thanks for that timely response.

Not necessarily. Seems like Corsair ram will often run in a stable fashion when overclocked to the next step up over it's advertised rated speed. But as a general rule, your conclusion is correct. You certainly can't count on memory running at the next step up if you try to overclock it. What you need to realize is that most memory's advertised max speed already is the overclocked profile. So when you buy memory advertised, for instance, as 1600 mhz memory, it actually is 1333 mhz memory in normal mode but will do 1600 with relaxed timings and/or more volatage. 1600 would be the "XMP" mode (xtreme memory profile) indicating it's overclocked.

X.M.P. is a intel standard and JEDEC is the normal memory standard.

wingman99 said:

X.M.P. is a intel standard and JEDEC is the normal memory standard.

Click to expand...

AMD CPUs may still be able to run the ram at the XMP frequency and timings, however they may have to be manually configured in bios.