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In my test desktop PC, I have motherboard ASUS P5K (specs link).

The specifications say: "Supports Intel® next generation 45nm Multi-core CPU".

Which CPU should I buy to get the maximum power from this motherboard? The configuration has 8GB of RAM, and all I am missing is the top CPU for this box to get the maximum use out of it.

Thanks for you time and advises

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closed as off topic by Journeyman Geek, RedGrittyBrick, Sathya Nov 5 '12 at 15:25

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A vage reference like Support Intel® next generation 45nm Multi-core CPU is often made because the manufacturer want to indicate that future, as yet unreleased CPU's of that category should work. Sometimes this also requires a BIOS update.

First check which CPUs are supported. From the link you gave: I see the

  • Intel Socket 775 Pentium® 4 Processors (Old, slow, hot)
  • Intel Socket 775 Pentium® D (two old slow hot P4s on a chip)
  • Intel Socket 775 Pentium® Extreme (same old hot, but faster and more expensive)
  • Intel Socket 775 Core™2 Duo (core2 design. Faster and much less power used)
  • Intel Socket 775 Core™2 Quad (core2 design. 4 CPU cores)
  • Intel Socket 775 Core™2 Extreme

You want a core2 based CPU.

Next look t the available socket 775 CPU core2 CPUs: Wikipedia has a long list of core2(tm) CPUs.

If you want the fastest single threaded performance go for a chip with a high clock speed. If you want max performance go for the chip with the most cores. If you can combine those two then that is great, but often you will have to choose between higher rated, but fewer cores part, or a part with more cores. (More MHz and more cores usually mean more heat, thus the combination of those two is usually limited).

The fastest duo core is the Core2 due E8600 with 2 cores at 3.33Ghz, and a TDP of 65 Watt.

The fastest quad core is the Core2 quad 9650 with 4 cores at 3Ghz, and a TDP of 95 Watt.

With only 10% difference in clock speed, and double the cores I would to for the 9650.

Next, check that:

  • Check that your motherboard can supply up to 95 Watt
  • Check that your CPU cooling can move 95 Watt away from the CPU.
  • Check that your BIOS supports it. If it is supported by a newer BIOS than update this before replacing the CPU.
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Your ASUS P5K has a LGA775 socket, so the best processor available for it would be Intel Core 2 Quad Q9650 or Intel Core 2 Extreme QX9770 (much more expensive tho). I had a P5KC with Q9650, works like a charm.

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did you have to get a stronger on-cpu fan for Q9650? – JoeM Nov 5 '12 at 14:26
@JoeM - You can by the stock fan is design to cool the CPU at stock speeds. – Ramhound Nov 5 '12 at 14:27
@JoeM no, I did not. But I must say the stock fan gets really noisy during gaming, so a big silent fan would be recommended. – Paulius Uza Nov 5 '12 at 14:30

You can use any supported LGA775 socket CPU. There should be a document on the ASUS website that lists which CPUs that the ASUS P5K supports.

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