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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snakeoil - Tuesday, September 8, 2009 - link
what part of stock speed you don't understand?if you are going to compare 2 processors both must have a fixed stock speed, if you increase the frequency of one of them by 1Ghz over the stock speed that is illegal.
or either both have a stock fixed speed to benchmark or both are overclocked.
overclocking is the same it doesn't matter if it's auto overclocking or manual overclocking.
we the people demand justice.
we the people are not stupid.
Anand Lal Shimpi - Wednesday, September 9, 2009 - link
You may find that your desire for fixed speed comparisons will become difficult in the future. Both AMD and Intel are going to be embracing this sort of an approach to clock speeds.Overclocking is not the same as what is happening with turbo mode. Overclocking is not officially supported by the manufacturer, it is running a part faster than it was sold at in order to improve performance. If an application crashes because you've overclocked your chip too far that's no fault of the manufacturer.
Turbo mode runs the chip at a frequency it's guaranteed to work at, it's operating within spec. It simply re-allocates thermal resources; Intel could disable 3 of the cores and sell a Core i7 870 as a 3.6GHz single-core processor, or disable 2 of the cores and sell it as a 3.47GHz processor, or only disable one core and sell it as a 3.2GHz processor. Instead of making the end user choose, instead you get a dynamic processor that can configure itself in real time depending on the workload.
This is in stark contrast to AMD's Overdrive utility which is actually overclocking. The chips aren't validated at the overdrive speeds and you're thus overclocking. Lynnfield is validated at both its standard clock speed and its turbo speeds, just like Bloomfield. So long as you don't exceed the TDP of the chip, it will work at those turbo frequencies. The things that will prevent it from turboing were outlined in the article.
Once again, I am not increasing the speed of anything - Lynnfield is simply working as designed. Whether it's in a Dell machine or in a custom build, it will always work this way. It's what the end user will see the moment they turn on a Lynnfield machine. The end user would not see the same from a Core 2 or a Phenom II based machine.
Take care,
Anand
Jamahl - Wednesday, September 9, 2009 - link
The problem with this review is it has a bunch of graphs with intel cpus with speeds rated at a lot lower than what they actually are.When you show a graph of an i5 @ 2.66 gigahertz beating a 3.4 gigahertz phenom II, that is false and that is a problem. This cpu was not ever at 2.66 gigahertz for any of these tests was it?
I suggest there is a problem with your reviewer also, not to mention his attitude about 'having a laugh' because i brought up this point?
Anand Lal Shimpi - Wednesday, September 9, 2009 - link
Again, that is the default clock of the processor - in many cases (especially the heavily threaded tests) it will be running at that speed. Turbo mode is dynamic, it's impossible to put down exactly what speed the chip was running at as it'll change throughout each test.You might see the chip run at 2.66GHz for several seconds, jump up to 3.46GHz then down to 3.2GHz, up to 3.6GHz and then back down to 2.66GHz all in the course of a single benchmark. It's repeatable, but there's no way to display all of that in a bar chart.
Take care,
Anand
snakeoil - Wednesday, September 9, 2009 - link
What you are doing is cheating, and people is not stupid.you are saying that lynnfield is faster than phenom 2 because lynnfield is overclocked at least 600 mhz.
people is not stupid as you think, and what you are doing is outrageous.
if you are going to benchamark with turbo enabled then you have to overclock phenom 2 at least the same 600 mhz.
show some respect for your readers. or are you really on intel's payroll?
Klober - Wednesday, September 9, 2009 - link
I am usually very respectful on the AnandTech and DailyTech forums and comments areas, but you sir are exactly as stupid as you are claiming people "is" not. Please read the article from beginning to end before continuing on your unjustified tirade. The processor is being used as intended by the manufacturer - to not test it in this way would be a disservice to the engineers who designed it and the company that produces it.snakeoil - Wednesday, September 9, 2009 - link
if you dont want to disable turbo the overclock phenom 2 at least 600 mhz.just to be fair.
Gary Key - Wednesday, September 9, 2009 - link
"if you dont want to disable turbo the overclock phenom 2 at least 600 mhz.just to be fair. "
You do realize that it takes near zero or sub-zero cooling to run the 965BE in stable manner at 4GHz with a 64-bit OS. When I say stable, I mean 24/7 multi-tasking, not a CPUZ screenshot or a SuperPi 1M bench. AMD has not solved this problem with the current stepping.
Once again, and for the last time, Intel's turbo function is a standard feature of the processor. AMD will be offering the exact same technology in their next processor family.
snakeoil - Wednesday, September 9, 2009 - link
that's not true.we demand justice and fair benchmarks.
you are losing all credibility and these benchmarks are worthless and unreal.
goinginstyle - Wednesday, September 9, 2009 - link
How many times do they have to respond to you in a logical manner. You should be banned and in some countries that would mean a beheading for being so damn stupid.