Vengeance 8GB 4x2 1866Mhz 4GB usable problem

[NajamQ]

System specs :
CPU: Core i5 760
MB: ASUS P7P55D
RAM: Corsair Vengeance 8GB Dual Channel 1866Mhz (9-10-9-27-1.5v)
GPU: GTX 670
OS: Windows7 Ultimate x64
MB BIOS: 2101

Problem: RAM becomes half (4GB) at 1.5v but using 1.65v solves the problem of available RAM but System is unstable worried about high voltage on 1.5v spec RAM.

Other Settings include
BCLK: 187 (to get RAMs to 1866Mhz)

Voltages:
IMC: 1.20 (to get to 187 bclk)
DRAM: 1.65
PLL: 1.8
LOC: disabled

Everything else is on AUTO

Manually setting SPD has no effect, Using XMP Profile makes only 4GB usable.

One thing I noticed is Round Trip Delay becomes zero below 1.65v for CH(A).

Another Question is what is more preferable; AUTO voltages or Manually specifying them. The board varies voltages in set to AUTO.

Memtest86+ gives zero error on 1 hour wall time. But that is at 1.65v.

Any help is appreciated, Thanks.

 

[Woomack]

to the OCF

I would try higher IMC voltage ( 1.25V maybe ) or 9-11-9 timings. Just check if it helps.
If memtest is passing then it looks more like IMC or other issue.
Since it's SB/IB designed kit then I would set timings manually but it should work fine from XMP ( or on some higher voltage as in your case ).

 

[NajamQ]

to the OCF

I would try higher IMC voltage ( 1.25V maybe ) or 9-11-9 timings. Just check if it helps.
If memtest is passing then it looks more like IMC or other issue.
Since it's SB/IB designed kit then I would set timings manually but it should work fine from XMP ( or on some higher voltage as in your case ).

Thanks for warm welcome .

I didn't know about this kit being SB/IB though I again went back to roots for finding my max bclk and indeed the stability problem was coming from low IMC. 1.2500 Solved it. May be a notch more.

But still CPU is not handling RAM above 4GB at 1.5v. Is it safe to run these modules at 1.65v on daily basis ?