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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HexiumVII - Tuesday, September 8, 2009 - link
I must say that Lynnfield is the best stock processor ever. It will o/c itself without you having to touch it at all. Nearly perfect for the masses. I absolutely can't wait for the notebook incarnation.ClagMaster - Tuesday, September 8, 2009 - link
The performance of these processors is what I thought they would be based on your May Preview Article. Its great the NDA is lifted and we can now see what this processor can really do.This is hardly a Celeron. I know a troll in earlier Lynnfield/P55 that should be eating crow.
Apahutec - Tuesday, September 8, 2009 - link
Not sure what "core parking" priorities are (reduce power consumption by grouping tasks on active CPUs, or tune performance by taking into account cache trashing in scheduler decisions), but it sounds like it could even be beneficial on my Core 2 Quad: single socket, no HT, but two Core2 Duo (each with its own L2 cache) glued together.erple2 - Tuesday, September 8, 2009 - link
Sounds like it, but the logic that controls that on the CPU is on the CPU, and uses up a couple million transistors. That would require a re-spin of the Core 2 parts (which, given the P55 platform release, I think is a safe bet won't happen), however.Obsy - Tuesday, September 8, 2009 - link
I don't get how Turbo Boost ends "dual-core or quad-core?" I know that an on-die IGP is a selling point for the upcoming 32nm dual cores, but wouldn't they be clocked higher than these quads and have Turbo Boost too? There will be dual cores clocked higher than quads again. Or is Intel not clocking their dual cores past the speeds of quads?macs - Tuesday, September 8, 2009 - link
Would be interesting an article about P55 mobo with nf200 chip and 2 gpu...Ryan Smith - Tuesday, September 8, 2009 - link
We talked to NVIDIA about that scenario a couple of weeks ago. A NF200 chip would not make a significant difference in performance, which is why they're letting manufacturers go ahead and just split lanes with a straight-up bridge chip.Darkanyons - Tuesday, September 8, 2009 - link
Thanks for this great article!!Tomzi - Tuesday, September 8, 2009 - link
Do the PCIe controller's voltage demands impose stricter limits on undervolting in the case of Lynnfield processors compared to Bloomfield? I can run my i7 920 at stock frequncies undervolted to 0.9xx V VCore. How much voltage (power consumption) reduction can we expect from the an i5 750?This might not be a hot topic so close to the release of the new chips when everyone is focused on top performance comparisons but I've always been interested in undervolting/clocking and would like to see a more complete picture.
Tomzi - Tuesday, September 8, 2009 - link
750 and 870 undervolted by ~0.1V reported on silentpcreview.