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 Un-Core: Faster Than Most Bloomfields
A few years ago I had a bet going with AMD's Ian McNaughton. We were at an AMD event where the Phenom architecture was first being introduced and he insisted that the L3 cache was part of the memory controller. This didn't make any sense to me so I disagreed. Minutes later a presentation slide went up on a projector talking about how the L3 cache and memory controller were on the same voltage plane; that's what he meant. Ian laughed a lot and to this day he holds it over my head.
The moral of the story is in Phenom and later in Nehalem, the processor is divided into two parts. Intel named them the core and the un-core. The "core" of these multi-core processors is made up of each individual processor core and its associated private caches (L1/L2). The "uncore" refers to everything else: PCIe controller, memory controller, DMI/QPI and the L3 cache.
The uncore isn't as critical for performance but is made up of a ton of transistors; roughly 400 million in the case of Lynnfield/Bloomfield (more if you count the PCIe controller). In order to save power, Intel uses slower transistors that have lower leakage for the un-core. As a result, the un-core can't clock up as high as the core and runs at a lower multiplier.
Take the Bloomfield Core i7 975 for example. The core runs at 25x BCLK (25 x 133MHz = 3.33GHz), but the un-core runs at 20x BCLK (20 x 133MHz = 2.66GHz). The rest of the chips, including Lynnfield, have slower un-cores:
| CPU | Socket | Core Clock | Un-Core Clock |
| Intel Core i7 975 Extreme | LGA-1366 | 3.33GHz | 2.66GHz |
| Intel Core i7 965 Extreme | LGA-1366 | 3.20GHz | 2.66GHz |
| Intel Core i7 950 | LGA-1366 | 3.06GHz | 2.13GHz |
| Intel Core i7 940 | LGA-1366 | 2.93GHz | 2.13GHz |
| Intel Core i7 920 | LGA-1366 | 2.66GHz | 2.13GHz |
| Intel Core i7 870 | LGA-1156 | 2.93GHz | 2.40GHz |
| Intel Core i7 860 | LGA-1156 | 2.80GHz | 2.40GHz |
| Intel Core i5 750 | LGA-1156 | 2.66GHz | 2.13GHz |
Here's another area where Lynnfield is better than the lower end Bloomfields: its uncore runs at 2.40GHz instead of 2.13GHz. The exception being the Core i5 750, its uncore is stuck at 2.13GHz as well. Once again, only the "Extreme" Bloomfields have a faster uncore.
Lynnfield's Memory Controller: Also Faster than Bloomfield
Intel only officially supports two memory speeds on Bloomfield: DDR3-800 and DDR3-1066. Obviously we're able to run it much faster than that, but this is what's officially validated and supported on the processors.
Lynnfield is a year newer and thus gets a tweaked memory controller. The result? Official DDR3-1333 support.
Three Lynnfield memory kits (left to right): OCZ, Patriot and Kingston
The same sort of rules apply to Lynnfield memory kits that we saw with Bloomfield. You don't want to go above 1.65V and thus all the kits we've seen run at 1.5V for the stock JEDEC speeds or 1.65V for the overclocked modules.
Like Bloomfield, 1.65V is the max we'll see on Lynnfield
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lordmetroid - Tuesday, September 8, 2009 - link
I am using Linux!andrenb91 - Wednesday, September 9, 2009 - link
c'mon probably u still running windows for somethings...wine doesn't work owith every thin...i run liux on dual boot for years and still trying to make wine run fligh simulator x..which is the only game I play...remember, these benchmarkes are only for win bases pcs, in linux the history is diferent, see it at phoronix.com...james jwb - Tuesday, September 8, 2009 - link
is turbo boost on for the benchmarks?snakeoil - Tuesday, September 8, 2009 - link
yes they benchmarked with turbo boost, that is cheating because thats overclocking the processor at least 600 mhz and presenting the results as it were at stock speeds.that's abusing the reader's trust.
maxxcool - Tuesday, September 8, 2009 - link
Hahaha, you are just as much of a idiot here as on techreport snake! ... did you come here and claim to have proof that i5 will not run xp-mode to?hahahaha, your just sad that Amd did not come up with this feature 1st.
Jarp Habib - Tuesday, September 8, 2009 - link
"yes they benchmarked with turbo boost, that is cheating because thats overclocking the processor at least 600 mhz and presenting the results as it were at stock speeds.that's abusing the reader's trust. "
This statement is a load of bullcrap. Anand's intent is to present the benchmarks in a way reflective of the chip's standard performance in normal use- hence not manually overclocking for maximized performance. The processor's very design revolves on itself automatically shutting down inactive cores and boosting the speed of active cores, *regardless* of what the end user does to the chip in BIOS or what apps he's running. Since all you need to do to use Turbo Boost is just *install the CPU in your system* then benchmarks should be run with it enabled.
If you want to COMPLETELY level the playing field, then TurboBoost should be shut down, for both Bloomfield i7 chips and Lynnfield i5 AND Lynnfield i7, as well as future i3 and i9. Also, HyperThreading must be disabled from all chips, 3DNow!, SpeedStep, Cool N' Quiet, MMX and the entire SSE instruction sets. After all, each different type of CPU executes those standard instruction sets differently. And since the SpeedStep and Cool N Quiet instructions force the chip to underclock and shut off cores while at idle, they must be eliminated from testing as well, or they'll throw off your idle power consumption benchmarks.
Since you will be normalizing the clock frequencies as well, you can save time by only needing to test just one chip from each product line. I'm not sure just how you will normalize the clock frequencies of your test units *without overclocking or underclocking* some of them though. Perhaps you'll let me know?
Meanwhile, back in the real world...
Voo - Tuesday, September 8, 2009 - link
The difference is, that turbo mode impairs the possible benefit of overclocking the chip, while most things you enumerated do not.If you want to get the maximum out of the 860 you've got to disable turbo mode as we see in the review, so for everyone who'd want to overclock their CPU the most interesting test would be a comparison between the two chips both at their maximum stable performance. Which at the moment means disabling turbo mode as we can see.
erple2 - Tuesday, September 8, 2009 - link
A-HA! So really, you're just interested in the benchmark "What does the maximum overclock do", not "How does the CPU perform at normal operations". BTW, does disabling HT does improve overclocking a little bit, so should that also be disabled? Cool-n-Quiet plus SpeedStep may also affect overclocking capabilities. Should those be disabled? I fail to see the difference between what the GP said and your justifications.MadMan007 - Tuesday, September 8, 2009 - link
I'm not bothered by enabled Turboboost in a 'stock speed' review either but I would really like to see more sites run their benchmark suite with 3.6-4.0GHz (or higher) C2D, C2Q and Phenom II versus overclocked but non-Turboboost i5/i7. The reason is that this type of comparison would be most directly useful for the site's enthusiast readerships to know what the actual difference between *their rig* and an i5/i7 would be.Kaleid - Thursday, September 10, 2009 - link
Seconded.