Intel's Core i7 870 & i5 750, Lynnfield: Harder, Better, Faster Stronger
by Anand Lal Shimpi on September 8, 2009 12:00 AM EST- Posted in
- CPUs
Lynnfield's Turbo Mode: Up to 17% More Performance
Turbo on Bloomfield (the first Core i7) wasn't all that impressive. If you look back at our Core i7 article from last year you'll see that it's responsible for a 2 - 5% increase in performance depending on the application. All Bloomfield desktop CPUs had 130W TDPs, so each individual core had a bit more breathing room for how fast it could run. Lynnfield brings the TDP down around 27%, meaning each core gets less TDP to work with (the lower the TDP, the greater potential there is for turbo). That combined with almost a full year of improving yields on Nehalem means that Intel can be much more aggressive with Turbo on Lynnfield.
| SYSMark 2007: Overall | Dawn of War II | Sacred 2 | World of Warcraft | |
| Intel Core i7 870 Turbo Disabled | 206 | 74.3 fps | 84.8 fps | 60.6 fps |
| Intel Core i7 870 Turbo Enabled | 233 | 81.0 fps | 97.4 fps | 70.7 fps |
| % Increase from Turbo | 13.1% | 9.0% | 14.9% | 16.7% |
Turbo on Lynnfield can yield up to an extra 17% performance depending on the application. The biggest gains will be when running one or two threads as you can see from the table below:
| Max Speed | Stock | 4 Cores Active | 3 Cores Active | 2 Cores Active | 1 Core Active |
| Intel Core i7 870 | 2.93GHz | 3.20GHz | 3.20GHz | 3.46GHz | 3.60GHz |
| Intel Core i7 860 | 2.80GHz | 2.93GHz | 2.93GHz | 3.33GHz | 3.46GHz |
| Intel Core i5 750 | 2.66GHz | 2.80GHz | 2.80GHz | 3.20GHz | 3.20GHz |
If Intel had Turbo mode back when dual-cores first started shipping we would've never had the whole single vs. dual core debate. If you're running a single thread, this 774M transistor beast will turn off three of its cores and run its single active core at up to 3.6GHz. That's faster than the fastest Core 2 Duo on the market today.
WoW doesn't stress more than 2 cores, Turbo mode helps ensure the i7 870 is faster than Intel's fastest dual-core CPU
It's more than just individual application performance however, Lynnfield's turbo modes can kick in when just interacting with the OS or an application. Single threads, regardless of nature, can now execute at 3.6GHz instead of 2.93GHz. It's the epitomy of Intel's hurry up and get idle philosophy.
The ultimate goal is to always deliver the best performance regardless of how threaded (or not) the workload is. Buying more cores shouldn't get you lower clock speeds, just more flexibility. The top end Lynnfield is like buying a 3.46GHz dual-core processor that can also run well threaded code at 2.93GHz.
Take this one step further and imagine what happens when you have a CPU/GPU on the same package or better yet, on the same die. Need more GPU power? Underclock the CPU cores, need more CPU power? Turn off half the GPU cores. It's always availble, real-time-configurable processing power. That's the goal and Lynnfield is the first real step in that direction.
Speed Limits: Things That Will Keep Turbo Mode from Working
As awesome as it is, Turbo doesn't work 100% of the time, its usefulness varies on a number of factors including the instruction mix of active threads and processor cooling.
The actual instructions being executed by each core will determine the amount of current drawn and total TDP of the processor. For example, video encoding uses a lot of SSE instructions which in turn keep the SSE units busy on the chip; the front end remains idle and is clock gated, so power is saved there. The resulting power savings are translated into higher clock frequency. Intel tells us that video encoding should see the maximum improvement of two bins with all four cores active.
Floating point code stresses both the front end and back end of the pipe, here we should expect to see only a 133MHz increase from turbo mode if any at all. In short, you can't simply look at whether an app uses one, two or more threads. It's what the app does that matters.
There's also the issue of background threads running in the OS. Although your foreground app may only use a single thread, there are usually dozens (if not hundreds) of active threads on your system at any time. Just a few of those being scheduled on sleeping cores will wake them up and limit your max turbo frequency (Windows 7 is allegedly better at not doing this).
You can't really control the instruction mix of the apps you run or how well they're threaded, but this last point you can control: cooling. The sort-of trump all feature that you have to respect is Intel's thermal throttling. If the CPU ever gets too hot, it will automatically reduce its clock speed in order to avoid damaging the processor; this includes a clock speed increase due to turbo mode.
Lynnfield and its retail cooler
The retail cooler that ships with the Core i7 is tiny and while it's able to remove heat well enough to allow the chip to turbo up, we've seen instances where it doesn't turbo as well due to cooling issues. Just like we recommended in the Bloomfield days, an aftermarket cooler may suit you well.
Lynnfield: Made for Windows 7 (or vice versa)
Core Parking is a feature included in Windows 7 and enabled on any multi-socket machine or any system with Hyper Threading enabled (e.g. Pentium 4, Atom, Core i7). The feature looks at the performance penalty from migrating a thread from one core to another; if the fall looks too dangerous, Windows 7 won't jump - the thread will stay parked on that core.
What this fixes are a number of the situations where enabling Hyper Threading will reduce performance thanks to Windows moving a thread from a physical core to a logical core. This also helps multi-socket systems where moving a thread from one core to the next might mean moving it (and all of its data) from one memory controller to another one on an adjacent socket.
Core Parking can't help an application that manually assigns affinity to a core. We've still seen situations where HT reduces performance under Windows 7 for example with AutoCAD 2010 and World of Warcraft.
With support in the OS however, developers should have no reason to assign affinity in software - the OS is now smart enough to properly handle multi-socket and HT enabled machines.
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7Enigma - Wednesday, September 9, 2009 - link
"What you are doing is cheating, and people is not stupid."Hand meet Face..... Gentleman we have a winner! Could you please post a picture of yourself so I can make a T-shirt?
james jwb - Tuesday, September 8, 2009 - link
i wouldn't go that far at all, but look a few comments above for my feelings on this. The honest way to go about this, Anand, was to do this review as you have done, but have a page or two dedicated to clock for clock, and to state in bold letter that turbo mode was on for the benches in the current review. Do this and all is forgivenHave you stopped to think how well Turbo mode in Lynfield has boosted benchmarks compared to bloomsfield?
As i said, yep, nice feature, but i do not expect a site to fall for stuff like this, i'd do stock (turbo-crap) results like you have, because this feature is there and cannot just be ignored, but my interest would have been to present clock for clock results on other pages, and it should have been yours as well. You've done a disservice to the enthusiast here. I was loving Lynnfield in your review until i realised turbo was on, then i felt this review was 100% useless to what i care and want to know about - clock for clock, and it must be the same for a huge percent of your readers, who at this stage, some probably haven't even realized turbo was on in your results and are still salivating. All enthusiasts who like to overclock themselves and not have turbo trying to trick us in reviews want clock for clock, you left them out, that is serious cause for questioning what the hell is going on at Anandtech. Sure, for those here who run stock, the review suffices, but, well, i've made my point now i think...
This is the first real blunder i've seen on this site, but imo its a big one, and that blogger who hates you guys and posts up lots of stuff about your contradictions (to which so far i find all his posts false, the server blog guy, you know who i mean), today he'll have a field day on this one.
Anand Lal Shimpi - Wednesday, September 9, 2009 - link
I can add a disclosure saying that turbo mode was enabled, but this has always been the case for our Nehalem reviews. We always try to review products with all of their features enabled as long as they ship that way and they don't reduce quality (e.g. certain GPU driver optimizations in the past).While I'll gladly add a clock for clock against Bloomfield in a few tests, flip back to our Lynnfield preview if you want a preview of that (that chip could only turbo up by 1 multiplier - effectively making it a clock-for-clock comparison to Bloomfield).
Turbo mode in Lynnfield does help it against Bloomfield in the lighter threaded apps, do keep in mind that Bloomfield has turbo as well.
It seems like what you're saying is that you want the maximum overclock possible for all cores and as such you will definitely disable turbo mode. In that configuration, the only difference between Lynnfield and Bloomfield (from a purely CPU standpoint) is one channel of memory. As I've mentioned before, that one memory channel is not going to make a tremendous difference for the vast majority of users. But if this is what you're asking for, I can definitely provide it. I'm out in California this week for an unrelated product, let me get back and I'll include that data in my Core i7 860 review.
Take care,
Anand
james jwb - Wednesday, September 9, 2009 - link
thanks for the response, it's appreciated. I hold anandtech on a pedestal, and was just surprised not to see some clock for clock stuff for the overclockers out there. I haven't used a CPU at stock for 6+ years for my main rig, so clock for clock is very important, though as you've said, there won't be too much difference between bloomsfield and lynnfield, i'd still like to see it, though :)As for your comment below about how intel and amd will be changing things soon for the stock users out there, well, i think clock for clock will become very important for overclocker then in these reviews, more so than ever to find out how each cpu performs, or maybe i'm wrong!
ClownPuncher - Tuesday, September 8, 2009 - link
Why would they turn off a product feature when reviewing said product? Because PhII doesn't have it? That is like not including DX10.1 results for AMD in HAWX. Consumers usually buy products based on features, this product has an aggressive turbo boost.Gary Key - Tuesday, September 8, 2009 - link
"there you go, finally you said it.all the benchmarks have at least 600 mhz over the processor's stock speed.
that is outrageous, then if you want to compare the result with phenom 2 you have to overclock phenom 2 at least 600 mhz over stock speed.
just to be fair "
First off, it is fair as that is how Intel ships the CPU, turbo is an integral part of the CPU's operation and is a major feature, end of subject.
Second, the 965 BE is not going to run stable at 4GHz under a 64-bit OS without near or sub-zero cooling. The Phenom IIs continue to have a problem when approaching 4GHz with a 64-bit OS. AMD has not fixed it yet.
james jwb - Tuesday, September 8, 2009 - link
Sorry, but i disagree. You seem to have swallowed some genious Intel marketing crap here. Yes, it's a nice feature, but any CPU can overclock, all overclockers will overclock, and your results gloss over that benchmarks were using turbo. This is bad, and the first time i've really seen this site do something really biased, or just stupid, not sure which...I'm telling you now, a big percentage of your readers will see the results for the 920 and 750 as clock for clock comparisons and think its a very close game here, and it's not.
I'll forgive you once you do a clock for clock comparison, but i won't forget that you pushed turbo results and nothing else, and didn't put a warning big bold statements like you normally do for important info stating these are with turbo on. Watch all excitement for this review from overclockers dwindle if you do.
goinginstyle - Tuesday, September 8, 2009 - link
They had an entire section discussing turbo mode, comments were made in the results about the turbo advantage,and their system setup page clearly states turbo in turned on for both lynnfield and bloomfield. Read the article.james jwb - Tuesday, September 8, 2009 - link
the look at turbo is rubbish, we need clock for clock against bloomsfield.It's not in bold, its of that importance to state this for those who flick through, which you'll find many do.
And still, i have no gripe with the data presented so far (aside from it not being very, very clear that turbo was on), my problem is what has been left out, and that is - a lot of important stuff for the enthusiast who control his own overclock.
goinginstyle - Wednesday, September 9, 2009 - link
Look on page 9 under the system setup, it clearly states that turbo is enabled. It is mentioned several times in regards to the performance results. If you could read, you would have understood that TURBO was ON. Several pages of the article discussed the new Turbo mode and how important it is to the performance of the processor.I suppose because you have labeled yourself an enthusiast that means you should be treated special. I guess between you, SnakeOil, TA152H, and a couple of others we could hold a special Olympics in your honor. Wouldn't that be special?
What is amazing, is that after reading several other reviews, it appears only Snakeoil at Tech Report is posting the same crap there as he did here. Everyone used Turbo mode in testing so why are you not posting at the other sites about how mistreated you are as an enthusiast.
Probably around 98% of computer owners do not overclock so why is it so hard to understand the testing methodology used here and elsewhere. For those of us that do not overclock, this article was perfectly suited for us and shows that we can get similar performance without opening up the box. Even for those who do overclock, they at least showed clock results and I am sure we will see more based on Anand's comments this morning.