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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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?