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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erple2 - Tuesday, September 8, 2009 - link
[quoting]Not only did the feature that provided the least benefit (triple vs. dual channel) drive the reason for the socket/pin count difference, they gimp the platform with superior tech by cutting PCIE lanes in half[/quoting]
I thought that the X58 has the PCIe controller on the mobo, and the P55 doesn't? That the Lynnfield CPU's had a built-in PCIe controller, whereas the Bloomfields lacked the built-in PCIe controller? That appears to be another reason why intel had to make 2 separate sockets/platforms.
Now, whether that was made intentionally to force this issue with multiple platforms is a side issue (IMO). I don't necessarily think that it's a problem.
JonnyDough - Tuesday, September 8, 2009 - link
"Personally, from a consumer standpoint, I feel Intel botched the whole X58/P55 design and launch starting with the decision to go with 2 sockets. Not only did the feature that provided the least benefit (triple vs. dual channel) drive the reason for the socket/pin count difference, they gimp the platform with superior tech by cutting PCIE lanes in half."I believe it was intentional and not a botch. Intel was trying to separate a high and low end and to sell more chipsets. It's Intel being boss. It's what they do. Confuse the consumer, sell more crap, and hope that AMD stays a step behind. This is why we need AMD.
Intel is good at marketing and getting consumers to jump on the latest trend. Remember the Pentium 4? Why buy a lower ghz chip when the P4 clocks higher right?
The educated consumer waits and pounces when the price is right, not when the tech is new and seems "thrilling". This review is great but no offense it still almost seems to come with a "buy this" spin - which may be the only way a tech journalist can stay privy to getting new information ahead of the curve.
Comdrpopnfresh - Tuesday, September 8, 2009 - link
You purposefully placing the possibility of overclocking solely in the hands of the lower chip, while completely disregarding the history and facts. This-or-that logical fallacy. Third option: You can overclock the higher-clocked chip too.Granted, I see your point about the hardware being of the same generation of the architecture; that lynnnfield is not the tock to bloomfield's tick (or the other way around if how you hear clocks starts mid-cycle) and therefore the silicon has the same ceiling for OC.
But bloomfield is a like a D.I.N.K. household; dual-income-no-kids. When you overclock bloomfield, not only do you have the physical advantage of lower heat-density due to a large die, but you also don't have the whiny pci-e controller complaining how timmy at school doesn't have to be forced into overclocking. The on-die pci-e controller will hinder overclocking- period.
Just like trying to overclock cpu's in nearly identical s775 motherboards/systems. The system with the igp keeps the fsb from overclocking too much. So then what- you buy a dedicated gpu, negate your igp you spent good money on, just to have your cpu scream?
Except in this case, if one were able to disable the on-die pci-e controller and plop a gpu in a chipset-appointed slot (sticking with the igp mobo situation in s775) you'd be throwing away the money on the on-die goodies, and also throwing away the reduced latency it provides.
Has it occured to anyone that this is going to open an avenue for artificial price inflation of ddr-3. Now the same products will be sold in packages of 3's and 2's? Sorry- just figured I'd change the subject from your broken heard still stick on overclocking.
chizow - Tuesday, September 8, 2009 - link
Actually in the real world, overclockers are finding the 920 D0s clock as well and often better than the 965s for sure (being C0), and even the 975s D0. You're certainly not going to see a 5x proportionate return in MHz on the difference spent between a $200 920 and a $1000 975. There is no third option because their maximum clock thresholds are similar and limited by uarch and process. The only advantage the XE versions enjoy is multiplier flexibility, a completely artificial restriction imposed by Intel to justify a higher price tag.
philosofool - Tuesday, September 8, 2009 - link
Not seeing it dude. A little overvoltage and LGA 1156 overclocks with 1366.chizow - Tuesday, September 8, 2009 - link
Yes and early reports indicate they will overclock to equivalent clockspeeds, negating any Turbo benefit Lynnfield enjoys in the review. That leaves less subtle differences like multi-GPU performance where the X58 clearly shines and clearly outperfoms P55.puffpio - Tuesday, September 8, 2009 - link
In the article you refer to x264 as an alternative to h264in fact, h264 is just the standard (like jpeg or png) and x264 is an encoder that implements the standard. i wouldn't call it an alternative.
that would be like saying photoshop is an alternative to jpeg, becuase it can save in jpeg format
puffpio - Tuesday, September 8, 2009 - link
"You'd think that Intel was about to enter the graphics market or something with a design like this."dun dun dun! foreshadowing?
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and since these parts consume less power yet are built on the same process, I assume they run at lower voltage? If so, since they ARE built on the same process, I'd assume they can survive the voltages of the original Bloomfield and beyond? eg for overclocking...
Anand Lal Shimpi - Tuesday, September 8, 2009 - link
Yes, Lynnfield shouldn't have a problem running at the same voltages as Bloomfield. The only unknown is the PCIe circuitry. I suspect that over time we'll figure out the tricks to properly overclocking Lynnfield.As far as Larrabee goes, I wouldn't expect much from the first generation. If Intel is *at all* competitive in gaming performance it'll be a win as far as they're concerned. It's Larrabee II and ultimately Larrabee III that you should be most interested in.
The on-die PCIe controller is a huge step forward though. CPU/GPU integration cometh.
Take care,
Anand
Comdrpopnfresh - Tuesday, September 8, 2009 - link
Have you seen bios implementations allowing for the controller to be disabled? Know if anyone intends to do this?