Problematic X48T-DQ6 Overclock

[Celox]

Hi there,

im having problems to keep my overclock stable.
I've been reading forums (mushkin, gigabyte,oc'er forum, guides etc) for weeks now without luck.

I hope someone has got an idea whats keeping it back.

First off my spec:
CPU: Intel Core 2 Quad Q9550
MB: X48T-DQ6 F5 Bios
RAM: 4x Mushkin 996601 (8GB RAM) XP3-12800 DDR3 - Mushkin Enhanced
CPU Cooler: Xigmatek HDT-S1283
Case Coolers: 5x Scythe STREAM SY1225SL12M @720rpm
Case: Antec 182p
GPU: ATI Radeon 4870 512MB (not oc'd)
HDD: SATA WD Velociraptor (GLFS) 300GB @ ICH9
HDD: SATA Seagate 1TB @ ICH9
PSU: Corsair HX620W

Monitoring done with Scythe Kaze Master and CoreTemp
Stability Test done with memtest86+ and Prime95 64bit
OS: Windows Vista Ultimate 64bit

My problem is that once i overclock it and run a Prime95 for over 12hours+ stable without any issues. On the next day i startup my rig when i get from work and do simple i-net researches and watching video clips and short avi's my system freezes and cracking sounds appears out of my headphones. :( Why is it stable for heavy processing on one day and on the other day it hangs on simple tasks?

Robust Graphics Booster___________ [Standard]
CPU Clock Ratio ____________ [8]
Fine Clock Ratio ____________[0.5]
CPU Host Clock Control_ [Enabled]
CPU Host Frequency (MHz)__________ [400]
PCI Express Frequency (Mhz)_______ [100]
C.I.A. 2__________________________ [Disabled]
Performance Enhance________________[Standart]
System Memory Multiplier____(SPD)__[4.00C]
Memory Frequency (Mhz)_____________1600
DRAM Timing Selectable_______ SPD __ [Manual]

CAS Latency Time________________ 7
Dram RAS# to CAS# Delay_________ 7
Dram RAS# Precharge Delay_______6
Precharge Delay (tRAS)__________ 18

ACT to ACT Delay (tRRD)_________ 5
Rank Write to READ Delay________ 10
Write to Precharge Delay_________ 24
Refresh to ACT Delay______________ 60
Read to Precharge Delay__________ 8
Static tRead Value_______________[Auto]
 Static tRead Phase Adjust________ [Auto]
Command Rate(CMD)_________________[2T]

CPU/PCIEX Clock Driving Control [800mV]
CPU Clock Skew Control [normal]
GMCH Clock Skew Control [Normal]

System Voltage Control____ [Manual]
DDR2 OverVoltage Control__ [+0.40V]
PCI-E OverVoltage Control_ [+0.10V]
FSB OverVoltage Control___ [+0.10V]
(G)MCH OverVoltage Control [+0.250V]
Loadline Calibration_______[Disabled]
CPU Voltage Control_______ [1.28750V]

CPU settings:
No-Execute Memory Protect [Enabled]
CPU Enhance Halt (C1E) [Disabled]
CPU Thermal Monitor [Enabled]
CPU EIST Function [Disabled]
Virtual. Tech [Enabled] (Im running multiple VMWare Workstation's for research purpose, im a systembuilder/system integrator for a living.)

I set my CPU Voltage Control to 1.28750V as i get a correct Core Voltage off 1.232-1.248 at Idle. Which is my VID 1.2500V.

[Nickel020]

This thread is a great resource for X48T DQ6 overclocking:
Gigabyte X48T DQ6 Living Review - Clunk's Forums.

Try increasing RAM timings. Especially tRead (aka tRD aka Performance Level). Use Memset to check your current value on auto and then increase it