Intel’s Core i5-655K & Core i7-875K: Overclocked and Analyzed
by Rajinder Gill on May 28, 2010 5:00 AM ESTi5-655K Meets a Cold Snap
Our dual rotary cascade is capable of holding -108 Celsius temperatures under full load from a Clarkdale processor clocked to 5.9GHz. For the i5-655K we’re kicking-off with Vantage:
Almost 200MHz behind the i5-661 in this test and around 100MHz behind our retail i5-540. Luckily for the i5-655K, this particular benchmark is not high on most peoples' agenda for Clarkdales. The real fun zone is Super Pi 32M:
Again, this comes in behind the i5-661, by around 250MHz this time. There’s nothing additional that the i5-655K offers over our 661 by virtue of its unlocked multipliers – at least up to this temperature. We tried various methods to squeeze more frequency and more performance out of the i5-655K, but were unable to find a better operating point than what we’ve shown here. QPI frequency is limited to around 4.8GHz on this sample, so the only way to really get the best from the chip is to keep QPI close to this level and provide a reasonable amount of memory access latency around the DDR3-2000 mark.
There is a bit of a reprieve for the i5-655K against the i5-540 however, because although the i5-540 manages 6GHz in this benchmark it scores poorly due to a maximum 23x multiplier needing a high BCLK frequency and thus a low QPI ratio to achieve this speed. As such, based upon everything we've seen here, our conclusion is that the performance of this particular i5-655K very much fits its price. There’s certainly enough on-tap to edge out the lesser i3 series in key areas, but we've not seen enough to believe they'll knock the better i5-660+ samples off the podium.
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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!