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
Discovery: Two Channels Aren't Worse Than Three
Intel told me something interesting when I was out in LA earlier this summer: it takes at least 3 cores to fully saturate Lynnfield's dual-channel DDR3-1333 memory bus. That's three cores all working on memory bandwidth intensive threads at the same time. That's a pretty stiff requirement. In the vast, vast majority of situations Lynnfield's dual channel DDR3 memory controller won't hurt it.
Move up to 6 or 8 core designs and a third memory channel is necessary, and that's why we'll see those processors debut exclusively on LGA-1366 platforms. In fact, X58 motherboards will only need a BIOS update to work with the 6-core 32nm Gulftown processor next year. P55 looks like it'll be limited to four cores and below.
Because of this, Lynnfield's memory bandwidth and latency cores are actually quite similar to Bloomfield. I used Everest to look at memory bandwidth and latency between a Core i7 975 and Core i7 870 (Lynnfield):
Lynnfield's memory controller is good, easily as good as what's in Bloomfield if not slightly better.
Both processors turbo'd up to 3.46GHz, indicating that Everest's memory test uses no more than two threads. The 975 ran DDR3-1066 memory (the highest it officially supports), while the 870 used DDR3-1333. The faster memory gave the 870 the advantage. Since we're not taxing all four cores, Lynnfield is at no disadvantage from a bandwidth perspective. Surprisingly enough, even SiSoft Sandra (which does use four cores for its memory bandwidth test) shows Lynnfield's dual-channel DDR3-1333 memory controller as equal to Bloomfield's triple-channel DDR3-1066 interface.
| SiSoft Sandra 2009.SP4 | Intel Core i7 975 | Intel Core i7 870 |
| Aggregate Memory Bandwidth | 17.8 GB/s | 17.3 GB/s |
Long story short? Lynnfield won't be memory bandwidth limited with DDR3-1333 for the overwhelming majority of usage cases.
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Griswold - Tuesday, September 8, 2009 - link
You definitely ARE stupid.dragunover - Tuesday, September 8, 2009 - link
Readers aren't, but you didn't read...snakeoil - Tuesday, September 8, 2009 - link
wow, this lynnfield is expensive, and the motherboards are expensive too.this is a crippled core i7 and you will have problems because the northbrige only have 2 x 8 pcie express electrical.
so if you are going to buy a new directx 11 video card don't commit the mistake of buying a lynnfield which is crippled.
without hyperthreading in some cases is a 40% slower than core i7
Eeqmcsq - Tuesday, September 8, 2009 - link
Anand, can't you just ban this guy? He's always trolls against Intel here, TechReport, and a couple other tech sites.JonnyDough - Tuesday, September 8, 2009 - link
I second the notion.Chlorus - Tuesday, September 8, 2009 - link
Thirded.maddoctor - Tuesday, September 8, 2009 - link
Your comment will not affect people whose committed to bought these. I think it is more valuable than any AMD platform. I don't think AMD will survive next year.TA152H - Tuesday, September 8, 2009 - link
From a purely processor perspective, I'd agree, but AMD platforms are pretty strong when you compare IGPs. The G45 compared to the 790GX is worse comparison than the Phenom II compared to the Nehalem.Don't forget IGPs are a HUGE market, so it's not an unimportant consideration.
PassingBy - Tuesday, September 8, 2009 - link
Yes, the IGP market is huge and Intel dominates that market as it is. If Intel can get its drivers right, then it looks like the IGP on Clarkdale/Arrandale will extend that domination. If you want to game seriously on graphics intensive games, then don't use an IGP.ash9 - Tuesday, September 8, 2009 - link
broaden your horizons; the real money is in corporate retooling- that said AMD's platform is without question offer more bang for the buck, considering corporate needs...most corporate folk have gone blind because of Intel's IPG's (laptops and desktops)Anand how bout running the tests that addresses that issue (IPG's and eye strain)