I am currently running the exact same motherboard and RAM. You can search the GSKILL forums for the ram and/or motherboard and find semi-decent information (I have posted a few times).
1. AMD Phenom II X4 965 125W 3.4GHz
2. Asus M4A89GTD PRO/USB3
3. Gigabyte GV-R485MC-1GI
4. GSKILL F3-12800CL8D-4GBRM x 1kit
Make the following changes under Ai Tweaker menu in the BIOS:
Ai Overclock Tuner - change to Manual
DRAM Frequency - change to 1600 MHz
DRAM Timing Configuration - change first 4 options and last option as follows
CAS# Latency - change to 8 CLK
RAS# to CAS# Delay - change to 8 CLK
RAS# PRE Time - change to 8 CLK
RAS# ACT Time - change to 24 CLK
Command Rate - change to 1T
CPU & NB Voltage Mode - change to Manual
CPU/NB Voltage - manually key in 1.2000
DRAM Voltage - manually key in 1.6000
I then went to the Tools menu and changed the O.C. Profile Name to Stock and saved it as Profile 1. These settings have given me very stable operation and were confirmed by GSKILL Administrators.
In fact, these settings were so stable, a simple manual key in of 20.0 for the CPU Ratio gave me a no-hassle, stable 4.0 GHz overclock (which I saved as 4GHz for O.C. Profile 2). Here is my CPU-Z validation link: http://valid.canardpc.com/show_oc.php?id=1410293
I typed this out while looking at the BIOS options and thought that anyone willing to build their own PC should be able to figure it out. But if you really need a screenshot or video, I can make one for you relatively easy. Just PM me.