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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strikeback03 - Tuesday, September 8, 2009 - link
How would you have graphics then? You would be limited to the 4xPCIe off the P55 on motherboards which support it, as there are no integrated graphics (yet)MX5RX7 - Tuesday, September 8, 2009 - link
I'm not sure that CPU/GPU integration is a good thing, from a consumer standpoint. At least in the short term.For example, in the article you mention how the majority of modern games are GPU, not CPU limited. The current model allows us to purchase a very capable processor and pair it with a very capable GPU. Then, when the ultra competitive GPU market has provided us with a choice of parts that easily eclipse the performance of the previous generation, we either swap graphics cards for the newer model, or purchase a second now cheaper identical card and (hopefully) double our game performance with SLI or Crossfire. All without having to upgrade the rest of the platform.
With the current model, a new graphics API requires a new graphics card. With Larrabee, it might very well require a whole new platform.
Ben90 - Tuesday, September 8, 2009 - link
Yea, im really excited for Larrabee, who knows if it will be good or not... but with intel kicking ass in everything else, it will at least be interestingWith overclocking performance seemingly being limited by the PCI-E controller, it seems like an unlocked 1156 would be pretty sweet
All in all i gotta admit i was kinda bitter with this whole 1156 thing because i jumped on the 1336 bandwagon and it seemed that Intel was mostly just jacking off with the new socket... but this processor seems to bring a lot more innovation than i expected (just not in raw performance, still great performance though)
chizow - Tuesday, September 8, 2009 - link
Was worried no one was going to properly address one of the main differences between P55 and X58, thanks for giving it a dedicated comparison. Although I would've like to have seen more games tested, it clearly indicates PCIE bandwidth becoming an issue with current generation GPUs. This will only get worst with the impending launch of RV8x0 and GT300.Anand Lal Shimpi - Tuesday, September 8, 2009 - link
PCIe bandwidth on Lynnfield is only an issue with two GPUs, with one you get the same 16 lanes as you would on X58 or AMD 790FX.If I had more time I would've done more games, I just wanted to focus on those that I knew scaled the best to see what the worst case scenario would be for Lynnfield.
In the end 2 GPUs are passable (although not always ideal on Lynnfield), but 4 GPUs are out of the question.
Take care,
Anand
JumpingJack - Thursday, September 10, 2009 - link
Anand, a few other sites have attempted SLI/Xfire work ... on in particular shows 4 GPUs having no impact at all on gaming performance in general -- well, 3 or 4 FPS, but nothing more than a few percentages over norm.Could your configuration with beta or just bad first release drivers be an issue?
Jack
JonnyDough - Tuesday, September 8, 2009 - link
Would it be possible to incorporate two GPU controllers onto a die instead of one or is that what they'll be doing with future procs? I would think that two controllers with a communication hub might supply the needed bandwidth of x16 + x16.Comdrpopnfresh - Tuesday, September 8, 2009 - link
with two gpu's being passable- do you foresee that applying to both two independent gpus, as well as the single dual-card gpus?Ryan Smith - Tuesday, September 8, 2009 - link
Yes. The only difference between the two is where the PCIe bridge chip is. In the former it's on the mobo, in the latter it's on the card itself.Eeqmcsq - Tuesday, September 8, 2009 - link
Talk about bringing a bazooka to a knife fight. AMD better be throwing all their innovation ideas and the kitchen sink into Bulldozer, because Intel is thoroughly out-innovating AMD right now.