2666Mhz DDR3 and Intel X79 chipset compatibility
Hi all,
I am new to this forum, but wanted to shed some light into the limitation in the compatibility between the new higher speed DDR3 desktop memory that has recently been released. Here is a list of 'facts' that will hopefully address some of the concerns some of you have posted:
1) The Intel Sandy Bridge (SB) CPUs are equipped with an Internal Memory Controller (IMC) that only supports up to 2133Mhz DDR3
2) The Sandy Bridge-E (SB-E) CPUs are equipped with an IMC that only supports up to 2400Mhz DDR3
3) The new Ivy Bridge (IB) CPUs are equipped with an IMC that supports DDR3 memory up to 2800Mhz
So, the bottom line is that you will NOT be able to make full use of 2600Mhz or 2666Mhz DDR3 when using a SB CPU with a Z77 motherboard or an X79 motherboard with a SB-E CPU.
How do I know this? Simple - I own a 16GB (4 x 4GB) set of G.Skill Ripjaws X 2666 Mhz DDR3 memory that I bought off of Newegg last week and have attempted to use it in my Intel SB-E 3930K CPU and Asus Rampage IV Extreme motherboard (with BIOS 1305) and was unsucessful in running the memory at either 2600 or 2666Mhz memory speeds. I tried both manual and XMP settings to no avail. I also attempted to use both stock voltages (1.65V) and higher and switched from 1T to 2T command rate, but nothing worked. In fact, my motherboard would not even POST when attempting to use either 2600 or 2666Mhz speeds. Once I reduced the speed to 2400Mhz, the motherboard POSTed and everything worked fine. I went ahead and reduced the latencies from the stock XMP settings of 11-13-13-35 to 10-12-12-31 as I was running the memory at lower speeds. Everything worked perfectly now, and I have my 3930K overclocked at a modest 4.5Ghz @ 1.36V with no other voltage adjustments made - a testament that the Asus IV Extreme motherboard is truly the shiznit!
Sorry for the bad news for those hoping to run the newer 2600Mhz and 2666Mhz DDR3 with their SB & Z77 or SB-E & X79 motherboard setups. I am very disappointed too. You might be able to squeeze out some Mhz (maybe even up to 2500Mhz with voltage tweaking/adjustments), but don't count on it. To give G.Skill credit, they do explicitly state that the memory is for Ivy Bridge and Z77 motherboard setups...something that I found out is indeed true