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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jasperjones - Tuesday, September 8, 2009 - link
Wonderful article as usual on AT. Read the articles on the website of your main competitor minutes before and didn't learn nearly as much about the LGA 1156 platform as I did here. Well done!I have one somewhat cheap comment. I always feel there's only one thing I do for which I really "need" my Core i7. And that's test-driving and debugging my well-threaded code (which makes use of OpenMP, MPI, threaded Intel MKL, etc.) before scp-ing it over to a cluster. Obviously, when testing code, I run using 8 threads. Still think that the Core i7 is probably more competitive in that area (performance/$ wise) than in the ones which this review focuses on (simply because I assume such code puts enough stress on the processors such that turbo-boosting is out of the question). On the other hand, I don't really care if gzip takes 2.5 or 3 seconds to compress a file (or if flac takes 8 or 9 seconds to encode my wav).
As I said, it's a cheap point. Just saying that I feel I primarily need "oomph" when running well-threaded stuff. Again, great article!
AeroWB - Tuesday, September 8, 2009 - link
Thanks for the interesting read, I do agree with some other people that some things are missing (clock for clock comparison) and some things are weird (core i7 with 1066DDR3). Some people are saying that everyone is overclocking their core i7, and while most readers of this article will probably be geeks that overclock I also read these articles as a systembuilder and I know that at least 95% of my customers don't overclock, so I really dig non-overclocked comparisons and results.There is also one thing I do not agree on, lets have another look at the page "The Best Gaming CPU?" and look to the DoWII results. What I see there is totally different from your conlusion though you do mention it in the text, the Bloomfield has lower minimum framerate then Lynnfield, but still your conclusion is Bloomfield is better then Lnynfield and Lynnfield is better then the Core2E8600. Ehm ???
Lets be clear the core i7 920 really sucks here as of its really low minimum fps you will have stutters. Great gaming is all about having a butter smooth FPS which dependent on the game type needs to be between 30 and 60 FPS. Basically the best game experience here will probably be with the E8600 as it has the highest minimum at 33 FPS which is great for RTS gaming. In order to say which CPU is best you should have an extra statistic like how much and how long the framerate dropped below 30FPS or something but as we do not have this data the minimum framerate is our next best thing. As weve seen before the Core i7 is good when using SLI/Crossfire but on par with the core2 when using a single GPU. Intel also told us themselfs that Core i7 was not made for gaming but for taking a bigger part in the server market. When increasing resolution/quality of gaming when using one GPU the Phenom 2 was often as fast and sometimes even faster then the Core i7. Unfortunately most CPU comparison with gaming are done at low to medium resolutions and quality so this effect couldn't be seen in most tests, but there were very few where this could be seen. So gaming with Core i7 920 only made sense when using SLI/Crossfire (as it scaled much better with these then Phenom2) or when paying the extra money (over Phenom2) because you used the system mostly for other task like video editing or so.
Now we can see this gaming problem of the Core i7 has been (at least partly) solved with Lynnfield, but still the Phenom2 965 has a higher minimum then the Core i5 750 so I would still prefer that one.
The other gaming test are not really relevant as all cpu's score a minimum of 60 FPS (ok one exception on 59) and so you won't notice any difference between all of the tested CPU's with those settings.
Still it is probable that the better gaming CPU in these test will also be better with higher settings, but as I have seen with the weird Core i7 / Phenom2 results I want to see tests with higher settings or test with more demanding games. And we want minimum and average results to determine which is best.
Sorry for the long post
iwodo - Tuesday, September 8, 2009 - link
I am waiting for SandyBridge or even Ivy Bridge for FMA.For now, a C2Q two years ago with money spent on graphics card will do fine.
The whole LGA socket and naming is a complete mess.
Dont get me wrong, it is a good Processors, but not the jump from Pentium 4 to C2D.
Money spend on SSD and Graphics is much better valued.
JonnyDough - Tuesday, September 8, 2009 - link
My dual core Opty 185 is still doing fine...Fallout 3 is still playable with my 8800GTS 640. The system has a slight OC and is chugging along at a minimum of 45FPS in the game on decent settings. Granted, it can't play every game - but I can only play one at a time anyway, and my life does not revolve around gaming. Hello...BEER PONG!Griswold - Tuesday, September 8, 2009 - link
I agree. I'll get excited when the 32nm dual cores with HT arrive. That would be a worthwhile "upgrade" (but a downgrade in number of cores, simply because I dont need 4 physical cores that much anymore) from my q6600 on a p35.Still, its a good product, just not worth an upgrade for everyone.
strikeback03 - Tuesday, September 8, 2009 - link
I was hoping there would be 32nm quads in this cycle, but it appears not. I'd definitely like something faster than my E6600/P965, but don't think it is worthwhile in time or money to just go to a C2Q.R3MF - Tuesday, September 8, 2009 - link
I spent much of the past year harping on AMD selling Nehalem-sized Phenom IIs for less than Intel sold Nehalems. With Lynnfield, Intel actually made Nehalem even >>>bigger<<< all while driving prices down.i think you mean smaller.
strikeback03 - Tuesday, September 8, 2009 - link
Nope, he meant bigger. Same process + more transistors = larger die, as is illustrated in the table.JonnyDough - Tuesday, September 8, 2009 - link
I think AMD realized years ago that they had awoken a sleeping giant, and it was a smart move to start thinking about competing graphically when they did. They saw how IBM had to change when Intel reared its ugly head. If you put all your eggs in one basket, you'll surely drop your next meal at some point. Diversifying into new markets was a smart move. Anyone who said that AMD didn't have good leadership didn't know what they were saying. Sure, money got really tight - but that's what has to happen to someone in a very competitive market at some point. Just take a look at GM. Giants crumble, little guys take over, and giants can muster a comeback...blyndy - Tuesday, September 8, 2009 - link
"I think AMD realised years ago that they had awoken a sleeping giant, and it was a smart move to start thinking about competing graphically when they did."That's an interesting thought.
I think there were to mains reasons why AMD acquired ATI.
1) in response to the news of Larrabee -- pre-emptive defensive move.
2)To diversify in preparation for Intels technological onslaught to finally kill its only CPU competitor.
So it may have been a smart move. On the other hand, knowing how patent riddled the CPU business is, maybe they could have ramped up R&D, but AMD is puny next to Intel.