I had 3x2GB of 998691 running fine on 1.62v @1500Mhz with 6-7-6-18-1T timings for a few years. My i7-920 was clocked to 3.2Mhz from rated 2.66Mhz.
Recently, I added 3x2GB of 998692 to make a total of 12GB of RAM installed. The system runs fine with BIOS set on Optimized Defaults with the RAM running on 1.50v @1066Mhz with 8-8-8-24-2T timings and the i7-920 running at stock 2.66Mhz. But any overclocking at all of CPU and RAM brings instability. I ran one pass of Memtest with the full 12GB installed with no errors. Did not test individual sticks. But in the past, each set of 3 sticks were installed in my system (separately at different times) and there were no errors or overclocking problems.
I believe that both 998691 and 998692 are the same except for the heat spreader design. Both are rated at 1600Mhz and 6-7-6-18-1T on 1.65v.
Can someone please suggest a way for me to get stability while all 12GB are installed and overclocking the CPU to 3.2Mhz and the RAM higher than 1066Mhz?
Before seeing your post, I decided to try XMP Profile 1. I have never used XMP before. It seems to have set QPI/Vtt at 1.41v. I manually adjusted BCLK to 150 and multiplier to X20. With Turbo on, CPU is running up to 3.15Mhz under load. Have at times used vDroop control on either Level 1 or on Auto. System seems relatively stable. with only one problem so far - on one occasion, I receved a Windows error message that Windows Manager (I think - might have been Windows Explorer Manager) failed to start. On most other boot ups, system runs fine, but still some Windows programs crash on occasion. With these settings, RAM is running at 6-7-6-2--2T @1500Mhz on 1.64v.
System boots but Windows will not start if I raise BCLK higher than 150. Am I doing something incorrectly by selecting XMP and then setting BCLK at 150 with 20 multiplier. (This seems to yield 1500Mhz for RAM rather than the 1600Mhz per XMP profile.)
Is QPI/vtt of 1.41v too high? Any other comments re: settings? Should I further adjust settings to get RAM to 1600Mhz? Should I change RAM command rate to 1T?
As mentioned above, I'm still seeing occasional instability with running applications crashing.