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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jonup - Tuesday, September 8, 2009 - link
Unfortunately people in corporate world do not make a difference between a HD4500 and a GX790. As lond as the Intel can display spreadsheets its good enough (or better) than a GTX295/HD4890X2, because it is Intel. You can change ignorance when it works.PassingBy - Tuesday, September 8, 2009 - link
My horizons are broad enough, thank you. The needs of many corporate desktops/laptops will be met by Clarkdale/Arrandale and no, nobody will go blind or suffer eyestrain (by virtue of the IGP anyway).PassingBy - Tuesday, September 8, 2009 - link
No edit function, so, as I point out later in the thread, people reading this review presumably won't be interested in IGPs anyway, given that these processors now have no IGP market. Wait for Clarkdale before trying to compare IGPs.dragunover - Tuesday, September 8, 2009 - link
Thanks for the review, if not as soon as I wanted it!Boobs McGee - Tuesday, September 8, 2009 - link
Do you guys have plans to do a motherboard review roundup for P55?If not, please do.
Gary Key - Tuesday, September 8, 2009 - link
I actually have three roundups planned, we have 15 boards here ranging from the $100 uATX items up to the $300 EVGA Classified series. We are only testing with retail products, released BIOS', and retail processors so the delivery of more than 70% of the boards late last week has created a small logjam. ;)The first article should be up on Thursday with a couple of my favorite boards and then a rather large one up on Monday and the last one a few days after that. Raja is working on a separate roundup of the top three boards targeted for the more extreme OC community. We will also have a P55 memory specific article shortly.
ClagMaster - Tuesday, September 8, 2009 - link
Looking forward to reading these P55 motherboard roundups.Anand Lal Shimpi - Tuesday, September 8, 2009 - link
Yes, Gary is nearly complete with his. Give him another day and it'll be up :)Take care,
Anand
Comdrpopnfresh - Tuesday, September 8, 2009 - link
By creating a new socket- they're providing a disincentive for early adopters of bloomfield. This chip is literally a humpty-dumpty that stands to benefit intel with everyone suffering a small loss of their own. The benefits of lynnfield vs bloomfield come from shuffling the architectural deck of nehalem. In reality, it only shows the possibilities of an inflexible architecture.The turbo mode isn't cutting it in day-to-day power consumption reduction. On the scale of a day, the average shmoe who is ass enough to leave a computer on for no reason gains no benefit. Lower the reach of a voltage plane, and reduce the number of components sucking juice, that only present benefits under certain situations (a third memory channel), and shmoe is happier.
If it was in the article, I apologize, but with the pci-e controller being on the un-core... what happens on a chipset with integrated graphics? Will the igp be linked to the processor now, rather than a bridge chip? If ati or nvidia made their own supporting chipsets with an igp- would the igp represent a chip onto itself, solely connected to the cpu, or would it have to work through dmi, and leave those on-die pci-e lanes for domestic usage?
It seems this is the warning rattle to nvidia that they chose their place with ion, and are stuck in it. When the change to 32nm comes, and the gpu is integrated into the cpu- what kind of robust 3rd party chipsets could exist in the budget end? Sure, you can always add a dedicated, off-die, gpu... but for budget boards used to eons of making room for a cpu and working a bridge chip around an igp- either horrible inefficiencies will creep up, or higher prices.
My money is on westmere having at least three power planes.
I'd like to know: with the pci-e controller on-die now... what impact this puts on graphics cards with higher on-card memory. Does it strengthen or minimalize it?
And, can the cpu now share the gpu's memory as a way to extend cache- after years of being forced to share the system pool. That 16gb/s link to gddr5 looks mouthwatering. I'd like to see performance tests run with the pci-e varient ssds floating around out there saddled to the on-die pci-e lanes, and a graphics card running off of chipset. Rather than elevating a horse-power driven graphics subsystem, I think the benefits of supplying more 'torque' by freeing mass storage ssds from the SATA interface would be far more substantial, and in all applications of the PC. You already have the means for nearly 2+2/3 times the theoretical bandwidth of SATA-6- which up til now seems rather bug-ridden and defunct.
Also interested in the outcomes of usb3 with this- as usb is built on the foundations of pci-e, is it not? If usb3 can allow for pci-e externally, and you remove the latency issue of usb signaling traveling from some peripheral bridge chip to the cpu, and just jack the usb3 communications into the cpu... could one use usb3 as a computer-to-computer psuedo qpi teaming/networking bridge for inter-desktop cpu communication. skip the entire bottleneck of client-level software implementation, and the subsystem communication buses for out-of-box signaling too...
plague911 - Tuesday, September 8, 2009 - link
The market just got a little more crowded so hopefully this will bring a reduction in prices of the 920. but..
“The Core i7 870 gets close enough to the Core i7 975 that I'm having a hard time justifying the LGA-1366 platform at all. As I see it, LGA-1366 has a few advantages:
1) High-end multi-GPU Performance
2) Stock Voltage Overclocking
3) Future support for 6-core Gulftown CPUs
“
Your exactly right 1366 I think is going to be be the best option to “future proof” my system however the new chips make the 920- seem a little low on features. With the goal of “performance on a budget” I feel like we are stuck either getting a board with a socket which wont compete in the future, or chip which is weaker than its lower class cousins. Unfortunately I dont see any of this being fixed in the next few cycles. Id like to see a low clocked gulftown (to save cost) feature rich with good OC potential thats on the lower end of the price scale. To me this would be a good follow up to 920 but but it dosent seem like that will be coming out for several cycles. Unless ofc i'm missing something which is probably the case.