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Is cool n' quiet better than speedstep?

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August 5, 2010 1:24:47 AM

I ask this because my friends Phenom II machine that he has overclocked to 3.6GHz idles at 800mhz where every Core 2 Duo I have seen, including my own seems to idle at about 2.4GHz.

Why can't intel go lower than 2.4?

More about : cool quiet speedstep

a b à CPUs
August 5, 2010 1:31:35 AM

It's really about the same. Clock speed is proportional to, but isn't the sole determinant for CPU energy usage.

An Intel 45nm Core2Quad actually idles with slightly lower energy usage compared to an AMD 45nm PhenomII x4.

Also, I see that your E8400 is overclocked to 3.7GHz - so you already have a very high FSB speed, which results in your high idle clock speeds. The PII x4 has lower bus speeds but a higher multiplier.
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August 5, 2010 1:40:05 AM

Interestingly enough, it idles at 2.4GHz with default everything and when overclocked idles at 2468mhz.

I seem to remember my 2.4GHz E2220 idle'd at around 1200mhz which is good, but I just don't see the point of them not lowering the multi even further.

It may only gain them a few less watts power consumption going from 2.4 to 800mhz but if you can do it, then why not?
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a c 99 à CPUs
August 5, 2010 1:56:05 AM

protokiller said:
I ask this because my friends Phenom II machine that he has overclocked to 3.6GHz idles at 800mhz where every Core 2 Duo I have seen, including my own seems to idle at about 2.4GHz.

Why can't intel go lower than 2.4?


The Intel Pentium M, Core, and Core 2 lines have a minimum SpeedStep multiplier of 6x. This yields idle speeds of the following:

100 MHz clock (400 MHz FSB): 600 MHz
133 MHz clock (533 MHz FSB): 800 MHz
167 MHz clock (667 MHz FSB): 1.00 GHz
200 MHz clock (800 MHz FSB): 1.33 GHz (desktop)/800 MHz (laptop)*
267 MHz clock (1066 MHz FSB): 1.60 GHz (desktop)/800 MHz (laptop)*
333 MHz clock (1333 MHz FSB): 2.00 GHz
400 MHz clock (1600 MHz FSB): 2.40 GHz

* PM45/GM45 laptop chipsets can reduce the FSB speed by half when the chip is at the minimum SpeedStep speed. This yields a nominal idle speed of 800 MHz in all of the chips. The 800 MHz FSB models run at a 100 MHz clock and an 8x (NOT 6x) multiplier, while the 1066 MHz FSB units run at a 133 MHz clock and a 6x multiplier.

You can see this with your chips. You have OCed the FSB to a 411 MHz clock speed to reach 3.7 GHz on an E8400 with its 9x multiplier. 411 MHz x6 =2.46 GHz, which is exactly what you said your idle speed was. Your E2220 has an 800 MHz FSB and is a desktop chip, so 200 MHz x6 = 1.20 GHz.

AMD chips work a bit differently:

- HT1 and HT2-equipped units had the core's lowest Cool 'n Quiet speed set at the HT link speed since the core could not clock lower than the HT link. This led to 800 MHz idle speeds (4x the HT clock, which is by stock 200 MHz) on most of the original Socket 940 units, Socket 754 units, and the original Socket S1 (S1g1) units. The later 940s as well as all 939s and AM2s ran at a 1 GHz idle speed (5x HT clock.) If you increased the HT clock to overclock the CPU, the Cool 'n Quiet idle speeds would also increase to 4x or 5x of the HT speed if Cool 'n Quiet was enabled on overclocked CPUs- sometimes OCing automatically disabled CnQ

- 65 nm original Phenom-class chips (Barcelona/Agena/Toliman/Kuma) had an idle speed of 1/2 the maximum core speed, so the idle speeds ranged from 900 MHz for the Phenom X4 9100e to 1.35 GHz for the Phenom X2 7850. These speeds would also increase as you overclocked the CPU to half of the overclocked CPU's top frequency.

- All of the 45 nm units idle at 4x the HT clock (which is still 200 MHz at stock), for 800 MHz at stock.
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August 5, 2010 3:05:26 AM

MU_Engineer said:
The Intel Pentium M, Core, and Core 2 lines have a minimum SpeedStep multiplier of 6x. This yields idle speeds of the following:

100 MHz clock (400 MHz FSB): 600 MHz
133 MHz clock (533 MHz FSB): 800 MHz
167 MHz clock (667 MHz FSB): 1.00 GHz
200 MHz clock (800 MHz FSB): 1.33 GHz (desktop)/800 MHz (laptop)*
267 MHz clock (1066 MHz FSB): 1.60 GHz (desktop)/800 MHz (laptop)*
333 MHz clock (1333 MHz FSB): 2.00 GHz
400 MHz clock (1600 MHz FSB): 2.40 GHz

* PM45/GM45 laptop chipsets can reduce the FSB speed by half when the chip is at the minimum SpeedStep speed. This yields a nominal idle speed of 800 MHz in all of the chips. The 800 MHz FSB models run at a 100 MHz clock and an 8x (NOT 6x) multiplier, while the 1066 MHz FSB units run at a 133 MHz clock and a 6x multiplier.

You can see this with your chips. You have OCed the FSB to a 411 MHz clock speed to reach 3.7 GHz on an E8400 with its 9x multiplier. 411 MHz x6 =2.46 GHz, which is exactly what you said your idle speed was. Your E2220 has an 800 MHz FSB and is a desktop chip, so 200 MHz x6 = 1.20 GHz.

AMD chips work a bit differently:

- HT1 and HT2-equipped units had the core's lowest Cool 'n Quiet speed set at the HT link speed since the core could not clock lower than the HT link. This led to 800 MHz idle speeds (4x the HT clock, which is by stock 200 MHz) on most of the original Socket 940 units, Socket 754 units, and the original Socket S1 (S1g1) units. The later 940s as well as all 939s and AM2s ran at a 1 GHz idle speed (5x HT clock.) If you increased the HT clock to overclock the CPU, the Cool 'n Quiet idle speeds would also increase to 4x or 5x of the HT speed if Cool 'n Quiet was enabled on overclocked CPUs- sometimes OCing automatically disabled CnQ

- 65 nm original Phenom-class chips (Barcelona/Agena/Toliman/Kuma) had an idle speed of 1/2 the maximum core speed, so the idle speeds ranged from 900 MHz for the Phenom X4 9100e to 1.35 GHz for the Phenom X2 7850. These speeds would also increase as you overclocked the CPU to half of the overclocked CPU's top frequency.

- All of the 45 nm units idle at 4x the HT clock (which is still 200 MHz at stock), for 800 MHz at stock.


Thanks for the long and informative post, if this forum had a rep system, you would be getting a ton.
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a c 99 à CPUs
August 5, 2010 10:57:28 AM

protokiller said:
Thanks for the long and informative post, if this forum had a rep system, you would be getting a ton.


Thanks! You can select my post as "Best Answer," which does give rep.
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August 16, 2010 8:10:01 PM

Best answer selected by protokiller.
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!