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.

Lynnfield's Un-Core: Faster Than Most Bloomfields The Best Gaming CPU?
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  • Supershanks - Thursday, September 10, 2009 - link

    Great Article Anand, I read it with great interest.
    However I found somthing that was strange and unexpected today
    My I7-860 was running at 30x133 3990 when running nucleus, that's according to cPU-z I have a link , but can't post http in this comment ?
    http://www.clunk.org.uk/forums/reviews/24295-asus-...">http://www.clunk.org.uk/forums/reviews/...-deluxe-...

    I'd appreciate your insight ?
    thanks
    Reply
  • Gary Key - Thursday, September 10, 2009 - link

    You need to change your version of CPU-Z. I have a screenshot somewhere around here of 48x133. ;) Reply
  • Scali - Thursday, September 10, 2009 - link

    On a slightly related note... With these new P55 boards I see that especially Asus uses a new line of onboard audio chips from VIA.
    I haven't really been able to find much info on these chips. I'd like to know how they compare to Realtek and other onboard offerings.
    Could you guys spend some time on reviewing the onboard audio next time you review one of these boards? Eg, what does the control panel for these chips look like, what features does it have (eg, can you have realtime encoding like DTS connect or DD Live?), what is the general driver quality like (proper support of 3d/eax effects etc)?

    I think that's what's been missing in general, the past few years. Onboard audio has gotten quite advanced, to the point where most people no longer use a separate soundcard (some boards actually come with some sort of X-Fi card). However, I rarely see onboard audio reviewed, only audio cards.
    Reply
  • agawtrip - Thursday, September 10, 2009 - link

    for me, i find this review is misleading if you are not a gamer - for i5-750 and PII x4 965.

    why?

    1. motherboard and video card - non-gamer dont buy sli/xfire board. onboard graphics is fine(780g/785g). for now, boards for i5 setup doesn't have onboard graphics. what will you do? you will be forced to buy a video card (maybe 4550/9400gt for $40).

    i5-750 - $195, GIGABYTE GA-P55M-UD4 - $150, nvidi 9400gt - $40
    --- TOTAL -------- $385

    PII x4 965 - $245, GIGABYTE GA-MA785GMT-UD2H - $90, no video card
    --- TOTAL -------- $335

    AMD setup is actually cheaper but slower. it's all up to you.

    2. power consumption - since you are forced to buy video card, it will consume additional power while AMD setup (780/785G) won't.

    well that's just my opinion.
    please inform me and the others if i given up wrong informatin
    Reply
  • chrnochime - Thursday, September 10, 2009 - link

    Or you can get a motherboard that's quite a bit cheaper:


    MSI P55-CD53

    http://www.newegg.com/Product/Product.aspx?Item=N8...">http://www.newegg.com/Product/Product.aspx?Item=N8...

    which is 120..

    or

    GIGABYTE GA-P55M-UD2

    http://www.newegg.com/Product/Product.aspx?Item=N8...">http://www.newegg.com/Product/Product.aspx?Item=N8...

    And yes I know these are NE prices, and that it might be more expensive/cheaper somewhere else
    Reply
  • Hrel - Wednesday, September 09, 2009 - link

    It DOES NOT have hyperthreading. Enabling it wouldn't increase the cost of the chip, it purely a political move. I HATE that! If a CPU maker has something that can increase the performance of my cpu, at no cost to them, then should enable it, at no cost to me. EVERY CPU should have unlocked multipliers. EVERY CPU should have hyperthreading. Reply
  • jnr0077 - Friday, July 27, 2012 - link

    hyperthreading steal ram from your pc i have a i5 750 + radeon hd 4850 it plays crysis 2 maxed the witcher 2 maxed skyrim maxed i think you need to read up on it before you comment :) Reply
  • PhilTaylor - Wednesday, September 09, 2009 - link

    FSX is well known as a CPU-limited game, it might be more interesting to test it then a GPU limited game like Crysis. For instance, the difference between 2 and 3 memory channels might have a greater impact on FSX, again due to its CPU-limited nature. Reply
  • cactusdog - Wednesday, September 09, 2009 - link

    A very good, detailed bunch of tests but there is a surprising lack of information regarding temps? Other review sites have done the same thing but there IS temp issues with these CPUs as with i7 1366 ones. That CPU at 4.0 Ghz on air will be around 90 degrees but little is said.

    Anandtech is more honest than most review sites (most of which are really just advertisements) but sometimes i get the impression that nobody wants to upset Intel.

    Reply
  • araczynski - Wednesday, September 09, 2009 - link

    ...bottom line to me, my E8500/crossfire setup still has plenty of gaming life left. I'll check back in a year. Reply

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