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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TA152H - Wednesday, September 9, 2009 - link
Your assumption would be wrong, I use computers for the normal stuff people do, and compiling.Go back to picking your nose, lowlife.
Skiprudder - Tuesday, September 8, 2009 - link
I'm starting to feel like some folks have Bloomfields and now they're trying to justify spending the money they did. At no point did Anand say Bloomfields were 'bad', he's just pointing out that due to current price/performance ratios the new chips are fantastic for the vast amount of folks here. They really area big step up for a lot of people, and frankly a lot of us feel we have better things to spend out money on than $300 X58 mobos. We can now get in on that sort of performance (or better) for a reasonable price, and how isn't this great?TA152H - Tuesday, September 8, 2009 - link
Well, you might be right, but within this context I'm going to assume you are talking about me, in which case you would be wrong.I don't have anything new, and I'm actually not going to get anything for a few months. Even if I did, I wouldn't let it cloud my perspective. Normally people who make these judgments are looking through their own personality flaws. I have many, but this is one area I do not.
Maybe I am annoyed at the processor because I was expecting more. I was expecting it to be a really nice processor, and it turned out disappointing. I get annoyed with stupid things sometimes, like the 4 clock cycle L1 cache irks me big time with the Nehalem. With the P55, the platform is just weak and I don't really like it when sites do everything they can to obfuscate the compromises in it.
I'll say this, though, about it, the power use is REALLY nice. I'm really impressed with that. Everything else though, just leaves me cold.
There are some questions that need to be asked, as well. Why is the P55 so damn expensive? It's the same cost as the P45, but without most of the logic.
Why is the 870 so expensive? Is there really any point to this processor at this cost? Maybe some, but not really for a broad segment of the buying population. I'd much rather have an LGA1366 if I were going into that type of expense, instead of the brain-damaged derivative.
LGA1366 motherboards are around $200 now, at least many are, so $300 is kind of an outdated number. For this, you get better i/o, better memory flexibility (you can use two or three dimms; you can't use three with a P55), better performance, etc...
Now, one thing Anand brought up, and I didn't respond to, was something about not needing more bandwidth unless you were tapping out all four processors. Needless to say, this is obviously false, and I wonder why he'd repeat it. A little thought would tell us that even with two cores running, you could gain advantages by having better bandwidth. The reason is simple. Let's say Core A and Core B are both plugging away, and Core A needs a memory read. OK, so it takes the bus, and starts the long process of getting a cache line read. Now, let's say a clock cycle, or two, or twenty, later, Core B needs memory outside of cache. So now it needs the memory bus. Hmmmm, but Core A has the bus. So, Core B has to wait. If you have three memory channels, you transfer data faster, satisfying the cache line faster, and freeing the bus sooner. So, now Core B can get it, and start working sooner. So, you could see better performance with lower processor use requirements than they indicate.
Now, the only possibility this premise is wrong is if the core only grabs 64-bit memory bank at a time, which seems very unlikely to me. In this event, there would still be one memory channel open to the second processor, thus no penalty would occur until three processors needed memory. I don't think this is what they did, as it would lower memory performance on the Bloomfield unless three processors were being used, and also, based on the shared L3 cache, it seems the entire memory bus is always used. Still, it is possible. Maybe Anand can answer this.
mesiah - Wednesday, September 9, 2009 - link
Dude, you are so full of shit they can smell it 3 states away. Don't you dare try to rationalize by saying "I was expecting more." Since lynnfield news first broke you have done nothing but trash the part, Call it brain damaged, and skew posted facts to fit your warped agenda. Then, when the retail part is finally unveiled, instead of eating crow (something you suggest Anand do) you act like every crazy half baked conspiracy theorist that ever existed and start ranting about biased reporting, facts being intentionally hidden, and flawed logic.While I will admit that this isn't the be all end all lynnfield review, this is day one of the launch. I believe more information was displayed in this review than can be reasonably expected for the initial review. In depth overclocking comparisons and the like will certainly come later, but that isn't to say overclocking was ignored.
You read the article and then go off on a tirade about biased reporting and the skewing of facts to meet an agenda when it is you that have been skewing facts all along, and you continue to do so. You make overclocking comparisons between lynnfield and bloomfield calling them similar, then ask why anyone would give up "all the other advantages" of the bloomfield if you are overclocking, but you fail to mention the big advantage for most, which is price comparison. Then later you try to rationalize price by quoting the lowest posted 920 sale price next to the 870 msrp. The parts hit the shelves today, give them a month for prices to normalize. You aren't going to get a smokin deal on the first one to roll off the production line.
Now, go ahead and call me a fool like you do everyone else that is smart enough to see you for what you are. Attempting to verbally abuse another person in order to make yourself feel smarter is a pretty common tactic for feeble minded people who are themselves afraid of looking stupid. Its the equivalent to bringing a gun to a fist fight just in case you start to get your ass beat. So, how about you stop being a pussy, eat a little crow, and admit that all of your talk about how terrible this part was going to be was wrong. Or better yet, just stop posting here because your pissy "I'm better than you" attitude does nothing but bring the site down.
You can reply and call me all the dirty names you want, you wont get a response. I only feed the trolls once a week.
TA152H - Wednesday, September 9, 2009 - link
Actually, you're an idiot, and you're changing my words to create an argument.I never said it was terrible, I said the pre-release performance was terrible, and I expected it to be better for the released version. It was, but I still don't think so highly of the processor, and I wouldn't consider it. I'd rather get the i7 920.
If you're going to argue, at least have the decency/intelligence to not misrepresent someone's position.
I didn't really read the rest of your crap. I could only skim through your sub-literate drivel. I doubt you would have said anything useful in it.
Skiprudder - Thursday, September 10, 2009 - link
Can you please stop referring to people as idiots and morons? I'm not sure where you acquired your rhetorical skills, but calling folks names is the last thing one should do if you're actually trying to convince people of your viewpoint. Call someone here a moron, and it makes you look like just a troll. Calm down, stay rational, and people will be much more likely to hear what you have to say (and if they aren't, why should you care anyway?) There's no excuse for rudeness.Skiprudder - Tuesday, September 8, 2009 - link
I agree, the 870 isn't priced at all sensibly (but I would argue the top Bloomfields are pretty darn unreasonable too). Prices are rather high right now, and it will be interesting to see what they do over the next few weeks as supplies and demands start to balance out.chrnochime - Tuesday, September 8, 2009 - link
The sad thing is, right now(at least), in order to get i7 CPU and decent MB to OC with, a P55 set up would run:~300 for the i7 860
plus
~200 for an UD4P or an Asus P55 Pro.
Whereas for a x58 setup,
I can get an i 7 920 for 200 pre-tax, and should spend about 230-250 for a decent motherboard.
So for me, it's actually cheaper to go with the x58 setup, even though P55 MB are supposed to be cheaper...
TA152H - Tuesday, September 8, 2009 - link
Yes, and you'd end up with better performance too. And better i/o, and better flexibility.Once you factor in overclocking, the P55 isn't really much of an option unless you go to it's really low end, where you simply can't build an x58. Then it's competing with the Core 2, and has a chance.
ClownPuncher - Tuesday, September 8, 2009 - link
Good article, thanks for the clarifications too.