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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Ph0b0s - Friday, May 28, 2010 - link
Not covered so much on these websites but I slurged on an I7 965 when I7's were new, becuase it was unlocked, even though I knew it did not have any extra head room than the cheap chips in the family. The reason I did this was so that I could use the I7's new turbo feature to overclock on demand instead of having to use static timings to overclock. With unlocked I7's and the right motherboard you can change the value of the turbo mulipliers to be more than just one or two steps.So for my chip if I have all 4 cores in use my turbo muliplier is set to x29 (3800 ghz, only using factory voltages at the moment) and higher amounts when less cores are in use. So when not doing anything my CPU clocks itself to 1.6 GHz and runs at 3.2 GHz if not doing too much and then clocks itself to 3.8GHz when extra power is needed.
So I really welcome Intel putting out these cheaper unlocked CPU's, as next time when I want to overclock using the turbo funtionality I won't have to fork out for an Extreme Edition again.
Also I would love to see more coverage of this type of overclocking that it is new with the Nathelems, Before it was only the I7 Extreme Edition chips that could do it, but now that are more options avaliable, maybe Anandtech could do an article taking about it.
Death666Angel - Friday, May 28, 2010 - link
Hello guys!I was really looking forward to Intel -K material. But the whole bunch of "i5 540" is more than an annoyance. It is downright embarrassing and I would urge you to re-read any future texts, as I am really not interested in reading stuff when so little time is put into the text. Really a shame since the content is looking good.
Rajinder Gill - Friday, May 28, 2010 - link
Sorry, blame me for that. Those skipped under the radar this morning.-Raja
Griswold - Friday, May 28, 2010 - link
If you wonder why Intel does this, it most likely boils down to two letters: BE. They were never priced as if they came straight out of Absurdistan. And perhaps Intel felt a little itch because of that...Maroon - Friday, May 28, 2010 - link
^^^we have a winner!DanNeely - Friday, May 28, 2010 - link
Where are you getting those numbers from? Software or are you using hardware to measure it directly off the mobo itself?Rajinder Gill - Friday, May 28, 2010 - link
Hardware measured using a clamp meter.Raja
DanNeely - Sunday, May 30, 2010 - link
So you were measuring the current going into the mobo via the 4/8pin 12V cpu power cable?Rajinder Gill - Monday, May 31, 2010 - link
Yes.DanNeely - Tuesday, June 1, 2010 - link
Did you also monitor the main ATX power connector to see if there was any increase in power draw there when overclocking?