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.

Homework: How Turbo Mode Works Lynnfield's Un-Core: Faster Than Most Bloomfields
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  • jnr0077 - Thursday, July 26, 2012 - link

    well i have the better model i5 750 1156 socket gaming score is 5.9 on basic 500 gb hd 7200 with a ssd it hit 7.9 on a gigabyte GA-P55A-UD6 12gb ram. as for the price
    cost was cheep intel (R)quad core (TM) i5 750 @2.66 GHz 2.67GHz cost around £100 mobo cost me £100 i though it is a very cheep upgrade considering price i wood like to here what score any Pehnom II X4 965 hit
    Reply
  • Milleman - Sunday, September 13, 2009 - link

    The article itself is good. But Why on earth compare a standard clocked CPU (AMD) against overclocked ones (Intel). Makes no objective sense att all. I's like having a car test between a standard car and a tuned racecar. Of course the racecar will win in performance. The overclock results shouldn't be there at all. Maybe as a remark that tell what will happen if one would like to overclock. Looks rather unfair and biased.

    So... why??
    Reply
  • Nich0 - Sunday, September 13, 2009 - link

    All I saw in this article is comparison of CPUs in their stock configuration. What's wrong with that? Reply
  • Bozo Galora - Friday, September 11, 2009 - link

    I must say this was a very good logical coherent review with just about all the info one would require

    Good job - I had no intention of getting one of these, but now I may change my mind
    Reply
  • IntelUser2000 - Thursday, September 10, 2009 - link

    http://www.intel.com/support/processors/sb/CS-0299...">http://www.intel.com/support/processors/sb/CS-0299...

    According to Intel...

    Core i7 870:

    5/4/2/2

    Core i7 860:

    5/4/1/1/

    Core i5 750:

    4/4/1/1

    So the i7 870 has higher Turbo mode for 3 and 4 cores than 860 does.
    Reply
  • Nich0 - Friday, September 11, 2009 - link

    Yeah and that means that the OC numbers for the 750 with Turbo don't make sense. For example 4160 / 160 = 26 which would be a Turbo of 6 BCLK.
    Same thing for the 860 OC 3C/4C Turbo number.

    Am I missing something?
    Reply
  • IntelUser2000 - Friday, September 11, 2009 - link

    Its likely Anand has ES versions or such which allows multiplier adjustments. But at stock, the linked speeds are the Turbo Boost grades. Reply
  • Nich0 - Friday, September 11, 2009 - link

    Yeah obviously I am not disputing the stock OC with Turbo enabled (that sounds weird: stock OC?), ie 160*20= 3200, but just what it means in terms of Turbo: it 'should' read 3.36 for 3/4C and 3.84 for 1/2C if the 1/1/4/4 Turbo spec is correct. Reply
  • rdkone - Thursday, September 10, 2009 - link

    I don't like the fact that the BCLK directly and synchronously communicates with PCIe buss, thus affecting the videocard negatively (among other PCIe cards)... This is like overclocking years ago whereas the PCI bus would be affected in the same way and causing headaches... This is a major issue I feel for those wanting to push a fairly big overclock on these CPU's... Intel screwed the pooch for us overclockers I feel... Just more justification to limp along with my core 2 quad at 4.1Ghz rock solid... Like others have said, is funny how the articles don't show older CPU overclocks against all this new garb... In the past they used to... But that hurts sales : ) Reply
  • SnowleopardPC - Thursday, September 10, 2009 - link

    Ok, so what type of boost do I get over a Q6600 with 8gb of ram and windows 7 64?

    Is it worth upgrading or waiting for that 6 core 32nm to come out next year?

    To upgrade to any of these I will need to replace a motherboard and ram with the processor.
    Reply

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