Overclocking Methodology Updated: Febuary 2nd, 2009
There's no one set of settings that will work for everyone. There's only a basic methodology to overclocking and it doesn't change regardless of platform you're on whether it be s939/AM2 or Intel 965P/975x/P35/X38/48/P45 or Nvidia 650i/680i/780i/790i. Even X58 follows the same method although the focus is much more on memory first as per brief general X58/i7 overclocking guide here
- Find your stable stock cpu/memory speed configuration settings. Yes that means to memtest86+ v2.11 and windows stability test (prime95/orthos/super pi/3dmark) you cpu and memory at stock speeds to confirm they're stable.
- Find the max stable memory overclocking frequency and timings/subtimings of your memory. To do this try to keep cpu FSB at stock speeds or as close to stock speed/FSB and use memory dividers where possible to find your upper limits of your memory frequency. Regardless, of platform memory clocks and timings/subtimings respond to mainly 2 types of voltages, vdimm memory voltage and NB - northbridge voltage. On some platforms such as Asus Commando/P5B Deluxe/P5K series and Striker Extreme they also may respond to vFSB and SB - southbridge voltages. X58 notes: memory responds to memory and uncore voltages. Uncore voltages are sometimes termed CPU VTT or on Asus QPI/DRAM voltages. Intel max spec'd uncore = 1.35v
- Next part is really a follow on from step 2, that is to find out your memory's max overclocking frequency and timings/subtimings with each memory divider to see if there are differences in internal latencies with each memory divider. Example, is on Asus P5B Deluxe 4:5 divider has a very very tight internal latencies compared to 1:2, 2:3, 3:5 on the Asus P5B Deluxe. This means while you could clock you memory to 600mhz on 2:3 divider with say 2.4-2.6v vdimm, you might need 2.4v just to get to 500-520mhz on 4:5 divider and that 500-520mhz on 4:5 divider might only be a fraction slower in performance than 600mhz on 2:3 divider. Each motherboard is different, so you need to test this for yourself. Again, the key is in 2 types of voltages, vdimm memory voltage and NB - northbridge voltage and basically how good your memory is. X58 notes: Core i7/X58 platform now uses memory multipliers x bclk to determine memory frequency speed. Most X58 boards will provide 6x, 8x, 10x, 12x, 14x, and 16x memory multipliers. So default Core i7 cpu has 133bclk. With default 6x memory multiplier = 133x 6 = DDR3-800Mhz speeds. Max frequency on X58 may vary depending on memory multiplier used as well. Higher the memory clock and sometimes bclk, means the higher the Uncore voltage needed. It's not uncommon to need 1.5-1.6v Uncore volts to reach >DDR3-1866 speeds even for manufacturer out of the box >DDR3-1866 rated memory.
- Next, is to find your max FSB frequency. That means dropping your cpu multiplier if you can and trying your max FSB at 1:1. From step 2, you would of already found your memory's max overclock frequency so bear this in mind when you are testing for max FSB at 1:1. Max FSB on core2 duo platforms respond to several different voltages depending on the motherboard and it's chipset they'd include vFSB, CPU PLL voltage, GTL+ Reference voltages and the most important of them for Intel 965P/975x/P35 or Nvidia 650i/680i at least is NB - northbridge voltage. Better Northbridge and Southbridge cooling (for Asus P5K series seeing as CPU PLL volts is tied with SB voltage on this series), may result in slightly better max FSB. X58 notes: Max bclk is determined by individual cpu, amount of Uncore voltage used as well as in some instances IOH/ICH voltages used. I suspect the motherboard design also helps somewhat but too early to conclude since I've only tested one X58 board - DFI UT X58-T3EH8.
- Regarding voltages and settings in bios in general, I usually start with AUTO values to initial tests, then retest stability and performance to compare with manually set values. Then for voltages I pick the lowest value I can select for manually setting the default voltages which I'd use for my base reference overclocks. I rarely will use AUTO voltages for the important voltages such as Vcore, Vdimm, NB and vFSB. Update: For P45 chipsets be careful of AUTO and even lowest selectable voltages for vFSB/CPU VTT, NB, CPU PLL etc and some P45 boards reported to auto jack up voltages as FSB rises and you could be using cpu killing voltages that you are unaware of!! X58 notes: For Core i7 /X58 key voltages are vcore, vdimm, uncore and to some extent IOH/ICH voltages. To keep cpu safe with greater than 1.65v memory voltage, the memory voltage must be within 0.5v of uncore voltage. Now some memory have XMP profiles which do all the voltage and memory settings for you automatically. Some manufacturer's XMP profiles set pretty higher uncore voltages like 1.5+ v especially for >DDR3-1866 rated memory. You may need more or less than that preset amount of uncore voltage. But I prefer to disable XMP profiles and manually test what voltages are needed. For 24/7, you'd want uncore voltage below 1.35v.
When you have tested for all 4 steps outlined above, you can then put it all together to find your optimal overclocks and test for overal system stability. This would require alot of reboots and testing with both memtest86+ v2.11
initially followed by windows stability tests - basically the same or similar procedure and applications I outlined for AMD64 Overlocking Guide AMD64 Overclocking Guide (07/11/06)
The above outlined steps you can see in action in nearly all my motherboard/cpu overclocking threads hence why I never really did an Core 2 Duo overclocking guide as basically every core2 duo cpu/board overclocking thread I started is a guide as such - all you need is to read the threads carefully
Some examples of the steps outlined include:
Note, not all threads follow the outlined steps fully since some of the steps are already done before hand i.e. you already know your cpus max FSB or max cpu mhz and/or memory's max overclocking frequency and timings/subtimings from prior tests with the same memory on the same motherboard. Hence, why I think memory overclocking is the most important part of the whole system overclocking process. Without good overclocking memory the rest of your system will suffer in terms of optimal overclocking potential.
If you have questions specific to your cpu/board/memory please DO NOT
private message me but rather start a new thread in the relevant forum on i4memory.com outlining your system specs, bios settings, bios version etc.