I bought a system with the GIGABYTE GA-MA790XT-UD4P motherboard, the AMD Phenom X4 910, and 2x2GB Corsair Dominator DDR3 chips.
> CORSAIR DOMINATOR 2GB PC1333 DDR3 PC3 10666 TRIPLE 2
The reason for this memory was that I already have 2x2GB Corsair XMS3 memory, so I wanted to end up with 8GB total.
-- CM3X2048-1333C9DHX / XMS3-1333 2048MB 1333Mhz 9-9-9-24 1.60V ver8.1
These two chips are supposed to be able to co-exist as they have the same latency and voltage (if I understand it correctly).
The problem is that the system was delayed a couple of times for backorder parts issue. So the manufacturer very gracefully upgraded my CPU to the new AMD Phenom X4 955 and the ram to 1600 Mhz for a very nominal fee. I ended up getting this: (it's in transit to arrive Wednesday).
-- AMD PHENOM II X4 955 3.0GHZ RETAIL
-- CORSAIR 2GB 16000MHZ CM3X2G1600C9D6
So my question now is whether the DDR 1333 memory I have is still compatible with the 1600 memory? Do I :
a) Just plug the extra memory and cross my fingers?
b) Down-clock the 1600 memory to 1333 ?
c) Overclock the 1333 to 1600?
The 1333 ram will work with the 1600 ram, with both running as 1333 speed. A different question that might be asked is why do you want 8 gig of ram? If you are using some very intensive, ram hogging programs, than 8 gig is good to have. But if you usage is mainly for games, and other light programs, the 8 gig will actually slow the computer down. The 8 gig will also mean lower overclocks, if you are into overclocking.
Personally, I would try running your new computer with the 4 gig of 1600 ram and seeing how it does. Use Task Manager to monitor how much ram you are using when you have it loaded up with the highest number of programs that you would normally run. If the ram use is less than around 3.5 gig, then stick with the 4 gig. Only if the ram usage is close to 4 gig would I bother to raise it. Further, when overclocking, the 4 gig of 1600 ram will cause less problems.
I do write with some experience, having 3 quad core computers at the moment and only using 8 gig of ram in one of them with does very intensive work. In the other computers, I find 4 gig of ram sufficient. 8 gig of ram may sound nice, but until and unless games get very big and demanding in the future, it is overkill for most of today's applications.
I am planning on (sometimes, rarely) running multiple VPCs at once on this computer when testing out software (windows 2003 Server vpcs running sharepoint, sql 2008, etc.). So the extra memory comes in handy.
I'm going to start with the 1600 at 4gb and see whats what.. Thanks!