Not my 1st Rodeo but I'm Confused - 2 vs 3 Sticks

I am now planning my every two-three year or so major upgrade from my current DDR2 system. Of course the new system will use DDR3 memory. I am considering an ASUS P8P67 PRO MOBO WITH AN I7-2600k.

I thought, apparently incorrectly, DDR3 memory could be configured with three sticks for optimum performance. This perception was reinforced when I noticed Newegg sells packages of three sticks.

Well, when I downloaded the manual for the ASUS P8P67, I was surprised to see it will only take a single stick or paired sticks. Obviously this is a subject I know a lot less about than I thought. When are a combination of three sticks used?

Intel socket 1366 uses three memory sticks, Ivy bridge will use four.
So far as I've read the 1366 platform never performed any better than the two stick ones memory wise.
Anyway socket 1366 and 1156 are "end of life" being phased out.
Your socket 1155 uses two sticks.
FWIW socket 1155 uses 1156 coolers, same hole specification.

I am not certain but I believe you can buy one more stick and run your three card memory. Some are single sided though, and I do not know if they overclock.

Normally I would look for 2X4GB DDR3 1600 CAS9 (or CAS8) memory as the best price/performance choice.

You really need to do some reading on current Sandy Bridge and memory used for it.

You have heard flooding in Thailand has driven HDD prices up 3 or 4 times what they were and shortages are expected for Q1 2012.

Woboy, Thanks

Based on what I have been learning this morning it looks like I am going to go with the Corsair Vengeance, 8 GB (2 X 4Gb), DDR3 1600 CAS8 at $78.00.

The spike in HDD prices are of no practical matter to me as the only HDD I will use will be the same 750 GB I now use for a secondary drive. I have been using Intel G2 SSDs for over two years now as a primary drive. I am probably going to buy a Samsung 830 120GB for this upgrade.

Yes sandy bridge uses dual channel as you already discovered. Those corsair rams are nice but I just picked up a set of 2x4GB CL 8-9-8 off the egg 2 days ago for $52.

1156 (X58 and such) was triple channel memory, and needed three sticks to run triple channel

I'm pretty sure that if you use 3 sticks on a dual channel system like P67 boards, either it won't run dual channel, or it will only see the sticks that it can run in dual channel, like A1&B1 or A2&B2 slots.

Don't take that to the bank because my memory (no pun intended) is murky on it, but check it out before you do it. Maybe someone will pipe up here that knows for sure



*Edit*

Here ya go, straight from the MaximusIV Gene-Z user guide. M4GZ is Z68 which uses the same memory config as P67:

"You may install varying memory sizes in Channel A and Channel B. The system maps the total size of the lower-sized channel for the dual-channel configuration. Any excess memory from the higher-sized channel is then mapped for single-channel operation"

I read that as you can do three sticks, but the stick not on the same channel (A or B) as the two that are, will be mapped for single channel. No good.

*End Edit*