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Core i7 Quad and TurboBoost tech question...

Discussion in 'PC Hardware' started by CrunchDude, 2010/09/12.

  1. 2010/09/12
    CrunchDude

    CrunchDude Inactive Thread Starter

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    I know that we are blessed to have some of the highest caliber experts when it comes to computer technologies who are members on this forum, so I'd like to ask what may sound like a couple of n00b-ish questions here.

    I recently read a couple of articles on the whole Quad vs. Dual core question and I was surprised to find that this is still up for debate. It sounds a lot like what everyone said over a year ago: Get the Quad now, so you'll have it in a year when most applications will have been rewritten to support multiple cores. Has that truly not happened?

    So isn't this is essentially the same thing all over again? One of the articles concluded that there are still a lot of people who will benefit more from a Dual-Core CPU with a higher clock vs. a Quad-Core processor with a slower clock but twice as many cores. It goes on to say that "...unless you're going to specifically use one or more of the few applications that support multiple cores in existence today, you will be better off going with a faster Dual-Core than a slower Quad ".

    Lastly, I'd like to get a better understanding of exactly how 4-core (or more) CPU's work.

    Specifically, will a Quad Core benefit me when I actively use multiple applications at once and have various different browsers open with 60 tabs between them and besides that, I have a bunch of stuff running in the background...would more cores really benefit me in this specific example? Or does a Quad really ONLY help when applications are specifically written to take advantage of more cores rather than less?

    Finally, just one more quick question if that's OK: If I had the choice between a Core i7-870 (2.93GHz, 3.46GHz w/ Turbo and Hyper-Threading, and 8MB L3) and a Core i5-680 (3.6GHz, 3.86GHz w/ Turbo, but no HT and only 4MB of L3 cache). What would be the better choice for someone who does not use Adobe CS5 and is not a gamer, but someone who does do a lot of multitasking...

    I thank you in advance for your expertise. I'm really hoping for some responses. Thanks again!
     
    CrunchDude,
    #1
  2. 2010/09/12
    Christer

    Christer Geek Member Staff

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    As a start, have a look at AnandTech Bench. The i5 is not the exact model but you get the general picture.
    Well, both are Hyper-Threading but one is quad core, the other is dual core (which is the reason for the different cache sizes):

    Intel® Core™ i7-870 Processor (8M Cache, 2.93 GHz)

    Intel® Core™ i5-680 Processor (4M Cache, 3.60 GHz)

    As I understand Hyper-Threading and Turbo Boost, you can't "have it all" at the same time. The processor has a limit on power consumption. If that limit is reached with all four cores running at the lower frequency, you may benefit from Hyper-Threading.

    (A dual-core with HT doesn't make it a "quad-core ". There are comparative tests out there but I'm a bit short on time right now. Go google and you'll find them.)

    If one or more of the cores is/are passive, the active core/cores can be stepped up to a higher frequency without reaching the power limit. In the case of the i7-870: 4 cores/8 threads at 2.93 GHz or 3 cores/6 treads at 3.6 GHz. In the case of the i5-680: 2 cores/4 threads at 3.6 GHz or 1 core/2 threads at 3.86 GHz.

    I had the same "brain storm" a few months ago when I built a system for a friend and he ended up with the Intel® Core™ i7-860 Processor (8M Cache, 2.80 GHz). He's doing a lot of PhotoShopping but I believe that the i7 is more "allround" than the i5.

    It also seems like the price is the same or in the same ball park and I would definitely go for the i7-870 if the alternative is the i5-680.

    Not "the whole truth and nothing but ", but a step on the way.
     
    Christer,
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  4. 2010/09/13
    CrunchDude

    CrunchDude Inactive Thread Starter

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    Hey Crister, thanks very much for typing this up. And yes, of course, the Dual-core i5's DO have Hyper-Threading. It is the Core i5 Quad's that do not. That all has to do with marketing, of course.

    Just like there is now an i7-880 (8M L3, 3.06GHz; Turbo up to 3.73GHz) which is double the price of both the i7-860 and i7-870, the latter of which are now within just a couple of bucks of each other. The same will likely happen later this year when the final Core i7-800 series chip will come out, the i7-890 (8MB L3, 3.2GHz; Turbo up to 3.86GHz), when the i7-860, i7-870, and i7-880, will all be around the same price. Intel is so predictable. lol

    One more question if I may. When you were weighing all of the pro's and con's with your friend a few months back, did either of you consider a Bloomfield instead of a Lynnfield?

    I wonder why the Lynnfield (i7-800) series can Turbo up significantly more than the Bloomfield (i7-900) series. I'm sure the fact that Bloomfield (and Gulftown for that matter) is running hotter than Lynnfield doesn't help that part of the equation. Did you ponder the whole DMI vs. QPI? How did cost affect your decision-making process?

    Thanks again for your help and I thank you for your time and effort once again! :)
     
    CrunchDude,
    #3
  5. 2010/09/13
    Christer

    Christer Geek Member Staff

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    CrunchDude,

    You're welcome ... :) ... ! (I was and still am hoping for some input from other members.)

    I don't think it's all marketing. As I said in my first reply, Hyper-Threading doesn't make a dual core a "quad core ". Depending on which application and what else is running, if my memory serves me correctly, there's a performance gain of 0-10 % comparing the same processor with HT disabled and with HT enabled.

    If a company buys and runs "hundreds" of the same computer, power consumtion is a factor that has an impact on the power bill. In that case, 25% lower power consumption might render the dual core with HT the better option over the quad core without HT.

    Oh yes, every business is predictable in wanting to extract the most from new products and as long as there are customers who "must have the latest" their strategy works.

    We did consider the Bloomfield but the additional cost was not in proportion to the performance gain. Not only the processor was more expensive but the motherboard as well.

    I compared two systems based on the same hardware (chassie, powersupply, etc), one with the i7-920 + 6 GB DDR3-1333 MHz + Gigabyte X58A-UD7, the other with the i7-860 + 8 GB DDR3-1333 MHz + Gigabyte GA-P55A-UD4. Both processors were selected below the price premium of being "new" and the system based on the Bloomfield was 25% more expensive than the system based on the Lynnfield. Worth it? Our decision was no!

    Not really. I became convinced that the memory bandwidth of a dual channel system wouldn't be saturated. I believe that I found some tests over at Toms Hardware that indicated this. Next ... :eek: ... my brain started to hurt!

    As I mentioned above, cost was a factor. We wanted a "noticeable" performance gain for our money, not just "bragging rights ".

    I have bought the hardware for a new build for myself. I use Office applications, Adobe Acrobat and other similar applications. Nothing decidedly processor or memory hungry but I do a bit of multitasking. My system will be based on the Phenom II X4 945 + 4 GB DDR3-1333 MHz + Gigabyte GA-870A-UD3 (the rest is the same as the Intel systems, more or less). The cost is ~70% of what my friend payed for the Lynnfield system and the fact that I don't do PhotoShopping or use other "demanding" applications, the cost/benefit equation brought me to AMD. I doubt that I will be disappointed, going from a 1 GHz Athlon and 133 MHz SDRAM with nine (9) years to its credit ... :p ... !
     
    Christer,
    #4
  6. 2010/09/14
    Christer

    Christer Geek Member Staff

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    I was pondedring the price difference between an i5-7xx and an i5-6xx. I thought it was small, bearing in mind that the 7xx is quad core and the 6xx is dual core. I checked the specs at Intel and when I read them, I remembered that the 6xx series have "traded" 2 cores for integrated graphics and HT.
     
    Christer,
    #5

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