i5 2.7GHz looks better than 3.1GHz?

Discussion in 'iMac' started by qap, May 6, 2011.

  1. qap macrumors 6502

    qap

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    #1
    Why the 3.1 is more expensive than the 2.7 if Intel price is lower for the 3.1 ($184.00) vs 2.7($216.00)? And why the 3.1GHz seems to be faster if the max clock is lower? Max Turbo Frequency 3.1 = 3.4 GHz vs 2.7 = 3.7 GHz and why the 3.1GHz have the same TDP (95W) as the i7 3.4GHz (95W) versus the "only" 65W in the 2.7GHz?

    I don't like these things… the 3.1GHz to me looks not (a lot of) better than the 2.7GHz. CHeck the comparison table by Intel: http://ark.intel.com/Compare.aspx?ids=52213,52207,52211,,

    Thanks.
     
  2. wordoflife macrumors 604

    wordoflife

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    #2
    The 3.1ghz is faster than the 2.7. Reason why 2.7 is more expensive is because it uses less power. not really an issue since this is an iMac opposed to a laptop
     
  3. qap thread starter macrumors 6502

    qap

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    #3
    How can be faster if the clock is lower (3.4ghz vs 3.7ghz) with the Turbo Boost and the same istructions? Maybe the 3.1 is faster with some apps that benefit from the all cores (a really few apps). The speed-benchmark like SuperPI or similar run in one core only, and the clock=the speed.
     
  4. Yorr macrumors member

    Yorr

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    #4
  5. Vylen macrumors 65816

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    #5
    It's because thats simply the design (or in other words, cause Intel made it so). The i5-2400 has a Turbo Boost stepping configuration of 1/2/2/3... the i5-2500S is 1/5/9/10...

    Also, keep in mind the i5-2500S is a low power model. Consequently, it would have a lower TDP. But since it's already low power, it can increase power throughput to increase the clockrate more so for Turbo Boost compared to the i5-2400 which is a standard power processor which has a higher TDP.
     
  6. qap thread starter macrumors 6502

    qap

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    #6
    Read above, Geekbench feature also the GPU points in the scores and also from the site:

    "Geekbench is able to measure the performance of all the processor cores in your system"

    But only few apps use all the cores and for that apps the clock is 2.7 vs 3.1GHz and the 3.1 is faster but when you use a normal apps with not multi-core support, you use only one core so the TurboBoost set the clock of the 2.7ghz to 3.7ghz and the clock of the 3.1ghz to 3.4ghz and 3.7ghz is faster than 3.4ghz.
     
  7. Spadoinkles macrumors regular

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    #7
    Hey there.
    What you are comparing is the i5 2400 (3.1GHz) vs the i5 2500S (2.7GHz)

    Unlike cars, S models are the reduced power consumption models of the non-S processors (i5 2500 which runs at 3.3GHz)

    First of all, clock rate really doesn't tell everything. Compare a 3.4GHz P4 with a 1.8GHz C2D and it'll tell you everything.

    From my experience (and others may otherwise question/rebuke/scream and throw tomatoes at), the performance of S models has been lessened to increase energy efficiency which is quite irrelevant when you're powering your Mac off the mains anyway. These are laptop processors and the S and T models are designed for macbook airs and extended use laptops that allow for greater battery life (remember they're all fighting for a realworld 24 hour lifespan...)

    Remember the 2500S supposedly sits above the 2400 range, possibly the reason why Turbo Boost kicks in to a higher clock speed. But 300MHz is barely noticeable anyway; I'd buy the 3.1 purely for the 6970M and not expect much of a bump in the CPU. If graphics isn't your main concern, I wouldn't spend all that extra on the 3.1 expecting any significant performance gains over the 2.7.
     
  8. Yorr macrumors member

    Yorr

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    #8
    Hmm.. than u have a good point. I purchased the 3.1Ghz cpu with a SSD combo. Maby more future proof in the end? Combined with the the 6970 (not available with the 2.7Ghz) was for me the +200 a good reason to move up.
     
  9. qap thread starter macrumors 6502

    qap

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    #9
    Ehm… I wrote "with the same istructions" (or architecture), the 2500s and 2400 have equal structure.

    and you have also more heat and watt :( I think it's better get the 2.7 with SSD or the i7 3.4 w/o SSD but I don't like the 3.1… obviously if you don't care about the gpu (better in the 3.1Ghz).
     
  10. qap thread starter macrumors 6502

    qap

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    #10
    In real benchmarks (thanks to tomshardware) the 2.7ghz and 3.1ghz have similar performance (a bit faster is the 3.1), with some tests the 2.7 (3.7ghz turbo boost) is faster than the 3.1 (3.4ghz turbo boost), depends if the test use all the cores or one only I think:

    For exapmples:

    Audio Encoding: iTunes 9.0.3.15 (wav to aac Audio)
    Intel Core i5-2500S (Sandy Bridge 4c) 2.7 GHz (Turbo 3.7 GHz): 64 sec
    Intel Core i5-2400 (Sandy Bridge 4c) 3.1 GHz (Turbo 3.4 GHz): 67 sec

    Archiving: WinZIP 14 File Compression
    Intel Core i5-2500S (Sandy Bridge 4c) 2.7 GHz (Turbo 3.7 GHz): 205.00 sec
    Intel Core i5-2400 (Sandy Bridge 4c) 3.1 GHz (Turbo 3.4 GHz): 211.00 sec

    PDF Creation: Adobe Acrobat 9 Professional
    Intel Core i5-2500S (Sandy Bridge 4c) 2.7 GHz (Turbo 3.7 GHz): 69 sec
    Intel Core i5-2400 (Sandy Bridge 4c) 3.1 GHz (Turbo 3.4 GHz): 71 sec

    Archiving: WinRAR 3.92 x64 File Compression (multi-threaded)
    Intel Core i5-2500S (Sandy Bridge 4c) 2.7 GHz (Turbo 3.7 GHz): 58 sec
    Intel Core i5-2400 (Sandy Bridge 4c) 3.1 GHz (Turbo 3.4 GHz): 62 sec


    Complete scores http://www.tomshardware.co.uk/chart...compare,2422.html?prod[4790]=on&prod[4792]=on


    In the other tests (GPU/video benchmark/multicore bench/etc..) the 3.1 is faster but there isn't a lot of difference, I think with OS X the difference for a normal use is small, more efficent should be add the SSD to the 2.7ghz model :confused:
     
  11. Spadoinkles macrumors regular

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    #11

    Hence why I said dishing out money for the 3.1, purely for the gains in CPU speed, is pointless. And waiting 2-3 seconds longer for a job to be done, really worth the $200-300 increase in price? I'm sure oyu could always spend the time you've saved working at McDonalds to get your money back...
     
  12. roland.g macrumors 603

    roland.g

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    #12
    I was looking at going with the 2.7. But honestly, the time gains on simple tasks that I don't use much, like audio encoding, zipping, etc. vs the 3.1 time gains in tasks that I use more often like Handbrake transcoding, the Handbrake video transcoding is significantly faster. 161 vs 182 secs. There doesn't seem to be any info on the test parameters like length of transcode source, etc, so I don't have a real sense of real performance, however, I looked at the full chart for that test and saw that my processor isn't on it - 2.8 Ghz Extreme X7900. But the 2.93 Extreme is on there at 456. So a 3.1 could presumably do it in 35% of the time, while a 2.7 would take 40% of the time of my current machine. That's up to 2.5 to close to 3 times as fast. And the 3.1 is 12% faster than the 2.7. But to tell you the truth, since most if not all of my library is transcoded, I am only really doing new titles. So having the time savings is not that crucial. But as my kids get older and we shoot more video, editing, rendering and such will be. And I suspect the advantages of the 3.1 will be there too. At the end of the day I would be paying $300 for beefier graphics though I don't game, a moderate to slightly quicker CPU depending on task, and knowing that both those items might provide me a slightly more capable machine as it ages.
     
  13. Spadoinkles macrumors regular

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    #13
    True that - while 2.7 may look a bit better on paper (and probably on your electricity bills) the graphics of the 3.1 isn't just for gaming - I've benchmarked the 6750M on the 6770M and 6970M and 6970's video rendering capabilities (and multitasking while rendering) are really improved. If you're looking at shooting and editing video you probably wouldn't be able to price the 6970M. CPU gains between 2400 and 2500S would be so small you should barely look at comparing it (the real world figures)
     
  14. qap thread starter macrumors 6502

    qap

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    #14
    CPU speed is nice but the 2500s has similar performance (than the 2400) with a lot of less watts and heat… for me is important, especially because i will not play games, render or similar things but just normal things likes watch TV, film, internet, office, chat etc.. less watts - less heat - less rumor - less heat in the room.. Infact i have to choose between the 2.7 and 3.1 WITH the SSD only (for less noise and i don't need 1TB), but if the 2.7 is more silent, more cooler with very similar performance in the normal things, i will choose it (I can also use the other money for more RAM…)
     
  15. raysmd macrumors member

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    #15
    so, then it's between the i5 2.7 and i7 3.4. Which would you rather get?
     
  16. iamthedudeman, May 6, 2011
    Last edited: May 6, 2011

    iamthedudeman macrumors 65816

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    #16


    The 2500S is not a laptop processor. Is has lower power, but in my opinion is the biggest bang for the buck in the whole 2011 line up. In daily tasks it's higher turbo mode will should allow it to processes single and dual threaded tasks.

    It seems it is truely the better of the two. Less power and higher turbo mode. The high end 27 if you don't need the better GPU and don't game or don't need the option for the i7 the base 2.7 with the i5 2500s seems the better buy.

    I personally went with two models. I needed a replacement for my Office and got a high spec 27 with the i7, and a new one for the home is a 27 2.7 with SSD because of the 2.7 2500s.
     
  17. Spadoinkles macrumors regular

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    #17
    Well if you're on a budget 2.7 + SSD would bring you further than 3.4 without SSD. Or if you're one of those filthy rich buying up more resources than you need, get 3.4 + SSD :)
     
  18. iamthedudeman, May 6, 2011
    Last edited: May 6, 2011

    iamthedudeman macrumors 65816

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    #18

    Thanks for the info.
    I did exactly that, add the SSD to the 2.7. I think it is the biggest bang for the buck in the entire line up.

    After reading this, made my decision so much easier.

    http://www.tomshardware.co.uk/sandy-bridge-efficienct-32-nm,review-32091.html
     
  19. iSayuSay macrumors 68030

    iSayuSay

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    #19
    The only reason people gonna buy hi-end 27¨ iMac (standard or i7 option) is the GPU, and the i7 itself of course.

    Drawback is the base 27¨ didn´t include i7 option, maybe because 95watt TDP prevent the iMac to do so, and IMO base 27¨ iMac use a bit lower PSU the same we´ll find on hi-end 21.5¨ iMac

    If you don´t game a lot, your option is the best. If :apple: indeed include GPU upgrade option to 6970M, the hi-end 27¨ would be meaningless
     
  20. iamthedudeman macrumors 65816

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    #20
    I don't know why they went with the 3.1 i5. My opinion is that the i7 should be standard on the high end.
     
  21. qap thread starter macrumors 6502

    qap

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    #21
    The i7 is worth for the extra money, extra heat and extra watts! Simply because IS (always) faster than 2400 and 2500S i5 ;) But if you don't use the i7 power and you don't run games on the iMac, the 2500S I think could be better, less expensive, less heat, more istant power (3.7GHz vs 3.4GHz) and less money :D

    Thanks for the info, I think I will do the same thing! Not only for the money, there are only 230€ (Europe) between the 2.7ghz and 3.1ghz but since I will use my mac only for listen radio, watch tv, internet, chat etc.. (at the moment I'm on iMac i5 2.8GHz quad-core the hi-end of the mid-2010 iMac) the 3.1 makes more heat (for that more problems) and I don't need the power, so I will choose your identical setup!

    I agree with you.

    For the PSU, the big difference between the 21.5" and 27" is the power fort the screen, for example my iMac 2.8 i5 quadcore mid-2010 when the display is off use only 35-40Watt but when is on the power consumption raise to 150-160Watt, I think the PSU is the same between all the 27" iMacs, maybe a bit more powerful on the hi-end 27" but in the lower 27" i don't think is the same as the 21.5 Top
     
  22. Bartos88 macrumors member

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    #22
    Is there really going to be a noticeable heat and fan noise difference between the two?
     
  23. qap thread starter macrumors 6502

    qap

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    #23
    Heat yes.. infact the 2500S (65Watt) is installed in the -less heat dissipation- 21.5" iMac (all the CPU in the 21.5" are 65W).
    The fan noise/speed I don't know at the moment, I think at idle the fan rpm should be the same but the fan should run at high rpm less or/and late than the 3.1GHz.
     
  24. Spadoinkles macrumors regular

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    #24


    Wow, upgrading from a 2010 to 2011 iMac just for that. Honestly I'd put that money somewhere else like a good sound system and all... your choice at the end of the day but that mac would be good for another 3-4 years what you use it for :/
     
  25. jborko macrumors member

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    #25
    See comparison table here and you'll understand:

    http://marketingtactics.com/Speedmark/

    3.1 is better with processing tasks... (mostly work with Video and Games), but according to the data I see it is only slightly better than the 2.7 so I will go for the latter one.
     

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