RAM modules, less or more for same GB?

[sebaz]

I'm getting ready to buy an Asus P9X79 Pro with an i7 3930k, and I'm trying to make a wise RAM choice, starting with the Asus tested modules. I want to get 32 GB, for which there is only one choice in that list, the Corsair CMT32GX3M4X1866C9, which is DDR3 1866, four modules.

However, the Intel website says this CPU only supports up to DDR3 1600. So checking the Asus list for that speed, I see the G.Skill F3-12800CL9Q-16GBXL, 16 GB, four modules, and since the Asus motherboard has eight slots, I can buy two of those and get to 32 GB for a lot less $ than the Corsair kit.

What I would like to know is:

1) Would using all 8 slots be the same regarding stability and speed than using four? (this is of course if I underclock the Corsairs to 1600, since it's the highest the CPU can handle apparently).

2) Does having twice the number of modules, especially Non-ECC RAM, mean twice the possibility of errors?

3) What happens if I get the 32 GB Corsairs and I don't underclock it to 1600 in the BIOS? Will this mean more chance of errors since the CPU says it can only handle up to 1600? Or does the BIOS automatically slows it down to 1600 when it detects that CPU?

Thanks

 

[redduc900]

Just because RAM isn't listed in the Memory QVL (memory specifically tested by Asus) for that board, doesn't mean that it isn't compatible. And that board supports up to DDR3-2400+, irregardless of what Intel spec's as the max. DRAM frequency for the Ivy Bridge CPUs. Just remember that the greater number of modules combined w/ higher DRAM frequencies and tighter timings = more stress on the IMC. This may require an increase in DRAM voltage, VTT (VCCIO voltage), looser timings, etc. to regain stability. With DDR3-1866 or higher installed, the BIOS will default the DRAM frequency to a lower value like DDR3-1333 or 1600. Meaning that you'll need to manually adjust the DRAM frequency to what the modules are rated at, or utilize the XMP Profile option in order for the BIOS to read the SPD info. from the modules to set the frequency, timings, and voltage automatically.

 

[Knufire]

Least amount of sticks possible is optimal.

1600 isn't the max, you can get up way high on Ivy Bridge. That being said, faster memory doesn't really amount to any real world performance increase.

 

[sebaz]

Least amount of sticks possible is optimal.

1600 isn't the max, you can get up way high on Ivy Bridge. That being said, faster memory doesn't really amount to any real world performance increase.

The 3930k is not Ivy Bridge, it's Sandy Bridge E. Regardless of that, on its product page on the Intel website it says it supports up to 1600. Now, I'm not a system builder and I don't have a degree in computer science, which is why I don't know if it's a problem to have a CPU that supports up to 1600 Mhz and the RAM is 1866 Mhz, or if it isn't.

But well, I'd rather be safe and go with QVL, so I'll get those four sticks and if I have any problems I'll lower them to 1600. I just hope that I'm able to install them fine because they seem to be pretty tall and my cooler, the CM Hyper 212+ is kind of gigantic.