Intel Core i7 920 overclocking (Asus P6T Deluxe)

Bit-tech.net folks posted an Intel Core i7 920 overclocking guide for Asus P6T Deluxe and MSI X58 Eclipse. However, the MSI X58 Eclipse blew some memory mosfets so the rest of the Core i7 920 overclocking guide was done on Asus P6T Deluxe motherboard.

Of particular interest is DDR3 memory voltage on X58 chipset based motherboards. Asus did scare us with their max 1.65v vdimm warning label earlier on. But it seems Anandtech.com’s comments were correct in that high vdimm voltage can be used only if the correct amplitude levels are maintained and a balance between bios core, DIMM, IMC, Uncore, and QPI voltages (and possibly multipliers i.e. Uncore clock multiplier being at least 2x times higher than the Memory clock multiplier set) are used. Pay attention to the QPI/DRAM Voltage (uncore) requirements in relation to DRAM voltage.

Some of the settings Bit-tech.net covered for Asus P6T Deluxe – BIOS Setup:

Note: The VDIMM within 0.5v of Uncore volt info was provided to Bit-tech.net by Intel

  • Intel Turbo Mode- Disable: We disabled it so as it would not interfere with the overclock, however we left on the new Intel low power states. Normally this affects how the CPU overclocks and in extreme cases we expect it will, because the on/off effect to the CPU frequency and voltages as the C-state changes.
  • BCLK Frequency – 200(MHz): BCLK = Base clock. This affects the QPI and uncore (L3 cache, northbridge) frequency too – some motherboards like the Intel Smackover allow the ratios to be adjusted, but the Asus does not. Here the ratio is 18x for the QPI and 16x for the uncore (northbridge/L3 cache). The uncore frequency must also always be below the QPI, we’re told.
  • DRAM Frequency – 1,600MHz: Although if you don’t have uber-ram, set it to the lower frequency as the bandwidth will still be super-sized regardless.
  • CPU Voltage – 1.35V: We found this was plenty, depending on your own CPU’s needs, it might be happy using less.
  • CPU PLL Voltage – 1.96V: In all honesty, we’ve got to play with this function more, but a 0.16-0.2V increase worked for Penryn so we’re also using it here.
  • QPI/DRAM Voltage – 1.35V: This is poorly worded by Asus – it should read uncore or QPI/memory controller voltage so not to confuse it with the actual memory voltage. Increasing this is also necessary as it helps overclock the base frequency as the uncore area overclocks increase in relation to the CPU core overclocks. This voltage is tied to actual DRAM voltage – the two are directly connected on the motherboard. You’ll need to increase this to keep the CPU safe. …. keep the CPU uncore voltage within 0.5V difference of the DRAM voltage and there’s no problem.
  • DRAM Voltage – 1.66V: This is the closest to the 1.65V the Corsair Dominator DIMMs wanted and it’s within the 0.5V Uncore difference.
  • CPU Differential Amplitude: A little extra (cpu) differential amplitude because Asus claims in the BIOS that it helps with overclocking and perhaps turning off some unused features like Virtualisation is worth it as well, but keeping the pre-fetchers and HyperThreading on will improve performance.

Read rest of the guide and results over at Bit-tech.net

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