i3-540 vs. i5-655K vs. i5-661

Next up, let’s take a look at the power scaling of the i5-665K against the more expensive albeit locked multiplier variant, the i5-661:

We’ve started the scale at 4GHz here, because any variance below this freqeuncy using water-cooling is negligible (around 2W in favour of the i5-655-K due to a lower VTT). The biggest gap we could find over 4GHz is 7 Watts which shows up between 4.1GHz and 4.2GHz where our i5-655K sample needs a rapid hike of VTT to scale. After that, there’s a 2~4W variance at equivalent frequencies favouring the i5-661 - not huge by any means over the frequency band of interest for overclockers using air or water cooling.

At this point, we’ll overlay the i3-540 power consumption figures using the same water-loop for cooling:

With good cooling, the i3-540 is plenty overclockable.

The i3-540 is at an “advantage” in this graph, as we’ve got no choice but to lower the memory multiplier ratio to 2:8 (giving a speed of DDR-3 1584 MHz at 4.554GHz). The i3-540 has a maximum core multiplier of 23x, and given the base clock needed to attain 4.55GHz, we’d be close to DDR3-2000 speeds which is a tall order for this particular CPU. Both the i5-661 and i5-655K are running the 2:10 memory multiplier ratio using a 25x CPU core mutliplier, giving a memory speed of DDR3-1820.

Before we have a quick look at the Lynnfield i7-875-K, one last thing we’d like to compare is how well the i5-655K handles sub-zero temperatures in comparison to the i5-661.

The capabilities of the i5-661 are well known to us, and we’ve already got a number of overclocking results on record to compare against. Given the i5-661 exhibits better frequency scaling relative to applied voltage, it’ll be interesting to see how the i5-655K fares…

Water-Cooling Clarkdale i5-655K Meets a Cold Snap
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  • wavetrex - Friday, May 28, 2010 - link

    In the table it sais $284 for the 980X, that MUST be a mistake! Reply
  • mianmian - Friday, May 28, 2010 - link

    In a previous Anandtech aritical, it was $999, maybe it is $824 now Reply
  • Texpat - Friday, May 28, 2010 - link

    I think the price for the 980x might be wrong. $1,000 would be closer tot he truth. Reply
  • ltcommanderdata - Friday, May 28, 2010 - link

    I'm really pleasantly surprised that the 2.93GHz Core i7 875K at $342 is cheaper yet has more features than the 2.93GHz Core i7 870 at $562. Although I'm guessing that's only temporary as the upcoming 3.06GHz Core i7 880 will probably take over the $562 price point, with the Core i7 870 dropping down to $284 and the Core i7 860 being phased out. There's also a Core i5 760 to replace the Core i5 750. Reply
  • DrMrLordX - Friday, May 28, 2010 - link

    You guys really busted out the big guns with the dual-stage cascade! Please do this more often when overclocking. I would love to see a C3 Propus at -100C (or a Thuban). Reply
  • jleach1 - Friday, May 28, 2010 - link

    On the second page, i believe in the 'test rig' table the proc is listed as a i5-870 instead of the i7-870 Reply
  • Rajinder Gill - Friday, May 28, 2010 - link

    Thanks - fixed! Reply
  • GeorgeH - Friday, May 28, 2010 - link

    "it’s full of talk about voltages and harps on about overclocking"

    No need to be shy about that - Anandtech is bookmarked because of awesome articles and analyses like this one.
    Reply
  • FlanK3r - Friday, May 28, 2010 - link

    not bad, my x6 1090T is full stable 4300MHz 2800MHz NB with aircooling ,-)...for games and benchmarks 4400-4450 MHz :) Reply
  • AstroGuardian - Friday, May 28, 2010 - link

    Guys, i think you should not hurry to release articles instead of taking them slow and sure. Many typos especially in the graphs.

    i3-530 vs i5-540
    Reply

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