Overclocking My Core 2 Duo 6600

 

CPU:

  • Bios Version: 1216
  • Stepping: 6/B2
  • Week: L647
  • Code: G431
  • Week: 33, Year: 06

 

Target: To raise CPU speed from 2.4 GHz to 3.6 GHz while keeping Load temperature at 60C or below, and passing ALL ‘torture’ tests and that includes passing the different temperature measurements found among the different torture applications.

 

Overclocked Settings:

 

  • PCI Clock Synchronisation: 33.33 (was auto).

 

  • Spread Spectrum: Disabled (was auto).

 

  • C1E Support: Disabled (was Enabled).

 

  • Memory (Cellshock PC2-6400 DDR2 CL4): Proved to be unreliable at stock motherboard voltage (even before I overclocked CPU). I increased the Memory Voltage to 2.25, after this memory was stable.

 

  • 4-4-4-12 @ 2.45 volts.

 

  • DRAM Frequency: Memory locked at 1:1 ratio, therefore it’s 450 (was auto).

 

  • PCI-E Frequency: Locked at 100mhz (was auto).

 

  • CPU Frequency: 450 (was auto). 450 x 8 (default multiplier is 9) = 3.6 GHz. Anything below 401 on an Asus P5B variant motherboard makes the Northbridge very overclocked. However from 401 upwards a lower ‘strap’ value is used and hence the RAM isn’t as fast as a 400 FSB speed invokes. But getting into the mid 400s makes up for this.

 

  • CPU Vcore Voltage: 1.5500 volts – (or 1.4960 volts as Bios Hardware Monitor reveals) was used.

 

  • Northbridge VCore Voltage: 1.55 (was auto/1.25)

 

  • FSB Termination Voltage: 1.4 (was auto/1.2)

 

This mix of CPU Vcore, N’Bridge & FSB voltages proved to be the most reliable. If I used the original ‘auto’ settings in any of them the system became unstable. I tried using a higher CPU VCore voltage without increasing the other voltages but this resulted in not only an unstable system but the temperatures were aprox 2 C higher overall.

 

Temperatures:

 

With water cooling temperatures are: Idle: aprox low 30’s. Load: 54-59.

 

Why the variety in temperature readings? I used some of the most reliable tools available (Intel’s Thermal Analysis Tool, Speedfan, Coretemp, and simulated loads with Intel’s Thermal Analysis Tool, Orthos, Prime95, etc), and the readings show the differences between their outputs.

 

Water Cooling Setup:

 

  • 2 double radiators on same loop. Radiators cool CPU, Northbridge, and Memory.

 

  • Upgraded cooling (which were originally either non existent or small, passive heat sinks), to active cooling on Southbridge and both sets of Power Regulators.

 

Graphics card isn’t overclocked nor does it have improved cooling. I don’t use my PC’s for gaming, and an NVidia GTS 8800 is more than sufficient for my needs.

 

Improvements for the Future?

 

On this rig I’d like to include another double or triple radiator, and maybe separate the loops so that the CPU has its own cooling loop. I’d like to get the load temperatures lower – although their values are currently acceptable. It’d make an interesting experiment to see if I could push the speed up to 4 GHz!

 

Further down the line on a future PC build, I’d like to water cool everything – both bridges, power regulators, etc. And I’d like to do this with 2 separate water loops.