Intel’s Core i5-655K & Core i7-875K: Overclocked and Analyzed
by Rajinder Gill on May 28, 2010 5:00 AM ESTWhen it comes to Intel processors, the word “unlocked” is not synonymous with low-priced mainstream products - it’s a feature normally reserved for flagship ‘Extreme Edition’ CPUs that bear higher price tags. Things are set to change today because Intel is launching the “unlocked” K series of processors to fit into the existing Lynnfield and Clarkdale line-up:
| Processor |
Core (GHz) |
Unlocked | Turbo Frequency (GHz) | Max Mem Clock | Cores / Threads | L3 Cache |
TDP |
Price |
| Intel Core i7-980X | 3.33 | Cores, DDR3, Power | Up to 3.60 |
3 Channels 1333MHz |
6 / 12 | 12MB | 130W | $999 |
| Intel Core i7-870 | 2.93 | DDR3, Power | Up to 3.60 |
2 Channels 1333MHz |
4 / 8 | 8MB | 95W | $562 |
| Intel Core i7-875K | 2.93 | Cores, DDR3, Power | Up to 3.60 |
2 Channels 1333MHz |
4 / 8 | 8MB | 95W | $342 |
| Intel Core i5-655K | 3.20 | Cores, DDR3, Power | Up to 3.46 |
2 Channels 1333MHz |
2 / 4 | 4MB | 73W | $216 |
| Intel Core i5-650 | 3.20 | DDR3 | Up to 3.46 |
2 Channels 1333MHz |
2 / 4 | 4MB | 73W | $176 |
| Intel Core i3-540 | 3.06 | DDR3 | N/A |
2 Channels 1333MHz |
2 / 4 | 4MB | 73W | $133 |
|
Intel Core i3-530 |
2.93 | DDR3 | N/A |
2 Channels 1333MHz |
2 / 4 | 4MB | 73W | $113 |
While it is interesting that Intel is offering unlocked core multipliers on Lynnfield and Clarkdale, it’s more interesting that the models being introduced are not the most expensive in their respective families. Especially considering that the i7-875K’s stock speeds are identical to the i7-870 while costing less. At $349, it's only a stone's throw away from AMD's 1090T, while you've got the i7-860 coming in cheaper than both. All of these processors can be compared to one another in Bench here and here.
Overclockers will sit up and take note at the prospects of increased flexibility and the potential of alleviating bottlenecks caused by insufficient bus margins on cheaper processors. We've all had CPUs that seem to have additonal headroom for frequency scaling, but are held back because the highest available core multiplier ratio is too low. We increase reference clock freqeuncies, only to find that some of the related busses aren't completely stable and as a result no choice but to fall back or relax key performance registers which defeats the purpose of performance related overclocking. That's one of the areas where the K-series might help. Another key factor that makes unlocked processors attractive is that they open the doors to easy overclocking for users that like to keep things simple. With unlocked multipliers we can overclock the CPU without having to fiddle around with memory ratios or memory timings, leaving those settings static.
As there are no under-hood changes to the substrates themselves, there’s not a whole lot of benchmarking for us to do in this review. We’ve already compared the performance of similarly clocked non K-series Lynnfield and Clarkdale processors in our platform launch articles and also have a range of comaprisons in Anandtech Bench. Our focus in this write-up is to look at how the i5-655K and i7-875K fit from an overclocking perspective against both their cheaper and more expensive counterparts.
Be for-warned that this isn’t a typical launch piece; it’s full of talk about voltages and harps on about overclocking in a way that will send many readers to sleep. If that isn’t a big enough deterrent, then read on…
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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!