RAM and Motherboard question

[CDN_Merlin]

I own an ASUS P8P 67-LE MB.
When I bought it I had 2 sticks of 4Gig Patriot CL9 RAM for a totla of 8 gigs

I just bought 2 sticks of Kingston 8 Gig CL11 RAM for a total of 16 GIgs.

I currently only have the Kingston RAM in using the first 2 banks of RAM( one blue and one black).

My question is thins, would it be prudent to install the other 2 sticks of 4 Gigs and if so, how would I put them in in terms of which slots?
Would I keep the 8 Gigs sticks in the Black slots or blue or what?

[Lothar]

I believe you're supposed to put paired sticks in the same color.

If the RAM is all the same speed, you should be able to install all of it without any trouble. If the 4GB sticks are of a slower speed, the mobo will treat it all as slow, which you probably don't want. Better to have 16GB of full-speed dual-channel RAM than 24GB of reduced-speed RAM that's being run in single channel mode.

Be aware that some operating systems (specifically Windows 7 Home) won't use more than 16 GB of RAM no matter what.

[CDN_Merlin]

The 16 gig is Case 11 and the 8 Gigs is Case 9 so they are faster. I have Win 7 Home Premium. And yep, it's limited to 16 Gigs. That's retarded. Guess I'll sell the 8 gigs.

[Krom]

Manual and quick start guides don't really spell it out, but apparently same capacity/matched sticks are supposed to be in same colored slots. For optimal performance it should be in dual channel mode, easiest way to tell would be to grab a copy of CPU-Z and look at the memory tab which should say "dual" in channels, if it doesn't you have the memory sticks installed sub optimally and you could improve your bandwidth by putting them the other way.

Do note when mixing memory of dissimilar cas latency, the slowest one wins, and often you have to go at further reduced latency/frequency to overcome compatibility issues or you will get bsods or the system may even refuse to post at all depending on how incompatible the two kits are.

That being said, the difference between the shortest cas latency and the longest cas latency amounts to <5% in any real world workload. DRAM is one of those things where as long as it is suitable for the system it is fast enough that the exact speed is irrelevant. The difference between slow and fast is totally insignificant compared to the penalty for simply not having enough.

(Also ditch the home edition of windows for pro and you will be able to use that extra 8 GB, although I'm on 16 myself and I rarely go over 30% utilization, so usefulness on this generation of software/hardware is questionable.)

[CDN_Merlin]

I ran CPU-Z and I'm in single mode. I will change the location of the stick to the other corresponding colour. I won't buy another version of Win 7 just to use the extra RAM.

[CDN_Merlin]

Funny that when I put both sticks in the Black slots (1&3) it wouldn't boot. Put them in the blue slots (2&4) and it works. Now running Dual channel mode.

Thanks