Intel’s Core i5-655K & Core i7-875K: Overclocked and Analyzed
by Rajinder Gill on May 28, 2010 5:00 AM ESTi3-540 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:
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…
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Rajinder Gill - Friday, May 28, 2010 - link
Hi,The actual "break point" is at 3.962GHz to be precise. A 9W step to 3.986GHz, followed by a 11w step to 4.009GHz. Anything higher than this and I'm loading up at 85C (according to DTS) and I can't get Linpack stable. I've extended x to show the 4.009GHz point. We'll endeavour to plot some more curves featuring some of the parts you mention if time allows.
Thanks!
Raja
Spenny2112 - Friday, May 28, 2010 - link
This only further confirms the change that the pc industry will be undergoing in the near future.Interitus - Friday, May 28, 2010 - link
Why does this make any sense on the 1156 platform? Intel created 2 different platforms, 1366 enthusiast and 1156 mainstream. Why is this on 1156 and not on 1366? Does that make any sense since 1366 is supposed to be the enthusiast/OC/hardcore version?Keep in mind I'm not arguing the viability of either socket. I'm just saying that Intel designed 1366 to be the high end, so why do this for the low end, but keep the unlocked chips for 1366 at $1k?
blandead - Friday, May 28, 2010 - link
1 reason that comes to mind first... $$$$$$2 this isn't targeted toward the enthusiast overclocker
the ones buying 1366 don't need unlocked multipliers to reach 4ghz or 1800+mhz ram speed.
I'm an AMD fanboy and my friend bought an i7 930 and 2000mhz ram and asked me to overclock it. I've never played with an i7 before, but surprisingly it was easy as cake to get it to 4.1ghz and 1850mhz ram on air and still have QPI overclocked past 6.4 dont quite remember i dont use the i7. Point is, with those achievements on a 930 I don't see a need for unlocked multiplier or k series.
TheBLK - Friday, May 28, 2010 - link
So why the messing BLK ????geokilla - Friday, May 28, 2010 - link
That's a huge jump in power consumption... But then these are engineering samples. I hope the retail ones will be better.Jamahl - Friday, May 28, 2010 - link
"This is another of those situations where we’ve had to make an eleventh-hour conference call with Intel to work out what and who these processors are aimed at."How about you make your own minds up instead?
First Anand did it with the awful clarkdale now you are doing it with these similarly awful cpu's. If intel gives you shit, TELL US ITS SHIT. Take a look around the web and see how poorly these cpu's were received elsewhere.
My respect for AT is at an all time low - there is no longer any pretence that you aren't an intel shill.
Hrel - Friday, May 28, 2010 - link
But it's about F***ing time!zodiacfml - Friday, May 28, 2010 - link
simply, the new unlocked chips does not offer real advantages compared to their siblings except for dynamic overclocking and the one posted which is little better turboboost speeds.yet, the additional cost compared to the performance of AMD's black edition processors is not that reasonable.
sergiu - Saturday, May 29, 2010 - link
It would have been nice if we could see the power consumption when dual cascade cooling has been used (both in stock and overclocking). I'm interested to see the leakage scalling with temperature!