2017 27" iMac accepts 2666mhz Ram.

Discussion in 'iMac' started by dannys1, Aug 12, 2017.

  1. dannys1 macrumors 68020

    dannys1

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    #1
    Testing with a 2017 iMac, thought i'd see if it'd take 2666mhz sticks and assumed it would and clock them down to the 2400 standard Apple advertises and sells, instead, it actually runs them at 2666 (reported as 2667mhz in macOS as it likes to round things up)

    Thought it might be interesting for some - I didn't run a benchmark on it yet but I will in the future - in the UK currently 2666mhz ram is actually cheaper (the 2400mhz have gone up 30% from retailers since the iMac launched)

    I suspect it'll run lower clocked ram easily too (the 2015 model did) and it'll probably run 3000mhz ram, if not at 3000, at 2666mhz no problems. So more options to shop around.

    [​IMG]

    [​IMG]
     
  2. EugW macrumors 68000

    EugW

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    #2
    Nice.

    Note though for most people they would want to keep their original RAM. Your method necessitates removing the original RAM.
     
  3. dannys1 thread starter macrumors 68020

    dannys1

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    #3
    Not really - if you want 64gb, order with 8gb and ditch it. You can't order with 32gb you'd get 4x 8gb sticks, so your option is buy 64gb from Apple or order it all yourself. I'm not sure why anyone would do anything but order with 8gb and pull them out (4gb sticks aren't worth much)

    The only way you'd ever keep the original ram is if you only wanted to upgrade to 16gb.
     
  4. EugW macrumors 68000

    EugW

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    #4
    I'd say over 90% of the people here keep the original RAM and upgrade to either 24 GB (original 8 GB + additional 16 GB) or 40 GB (original 8 GB + additional 32 GB). And a few do go for 16 GB total.

    I'm running 24 GB for example. And yes, with 24 GB, it still gets dual channel performance.

    So far I've only seen a couple of users (including yourself) that installed 64 GB. I'd guess it's less than 2% of iMac owners with 64 GB RAM.
     
  5. dannys1 thread starter macrumors 68020

    dannys1

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    #5
    Really? I don't think I could handle running a random number, would have to be 32 or 64.

    Also the 8gb ram is barely worth anyway, it's not like you're losing much by pulling it out - you can always sell it for the few quid it's worth on eBay anyway. Seen as you can buy the exact RAM Apple sells, i'd much rather pull it out and have all the same stuff inside too - you can put Vengeance in instead of the budget stuff Apple uses.
     
  6. EugW macrumors 68000

    EugW

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    #6
    Yes really. The fact you don't like those numbers is purely a psychological response on your part. However, it has no basis in reality, because 16 GB and 24 GB RAM will run at exactly the same speed if they have the same specs. As mentioned, 24 GB or 40 GB give dual-channel performance.

    Just check out the various memory threads. Most people are getting 24 GB or 40 GB.

    For most people 64 GB is way overkill, and therefore a waste of money for most (but not all) people. Even 40 GB is overkill for most, but more people can benefit from 40 GB.

    The sweet spot for the general population is probably 24 GB... which is 50% more RAM than 16 GB. 16 GB RAM becomes restrictive for even some mainstream users, but 24 GB will satisfy the needs of a lot of people who might feels slightly constrained by 16 GB. IOW, for the mainstream, the best bang for the buck is to get 16 GB aftermarket RAM and add it to the 8 GB of stock RAM from Apple for a total of 24 GB. And if you need more, then buy 32 GB of aftermarket RAM instead, and add that to the stock 8 GB, for a total of 40 GB. Realistically, the only scenario where it makes sense to ditch the stock RAM is if you need more than 40 GB.
     
  7. dannys1 thread starter macrumors 68020

    dannys1

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    #7
    Yes but you still don't know if you're putting ram in with the same timings - unless you're putting all the same type in. In real world it probably won't matter, but we're talking of like £30 difference to do it, so there's no real point to keep it in there. By the time you've pulled the 8gb out and bought a 32gb bundle (which are usually discounted) then sold the stock RAM it's probably cheaper to do it, you end up with more ram that is all the same.

    Anyway - that's completely off topic, the big discovery here is the 2017 iMac logic board is capable of running 2666mhz RAM, if anyone is genuinely interested in that and the performance boost it may or may not give, they sure aren't bothered by the stock 8gb.
     
  8. EugW macrumors 68000

    EugW

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    #8
    Crucial RAM runs at the same timings, if you select the RAM using their RAM selector. As do many other RAM modules.

    And no, it is not cheaper to get 32 GB RAM and sell the stock RAM than it is to just buy 16 GB RAM and go with 24 GB total.

    However, if you really do need 32 GB, then you may as well make it 40 GB, because you're not going to get much money on eBay for the 8 GB of stock RAM.

    Yes. It's interesting to hear.

    However, for those who need a fair bit of RAM, it's usually better to have 8 GB more RAM than the 1% performance increase that 2666 MHz RAM would provide.

    http://www.anandtech.com/show/8959/...-3200-with-gskill-corsair-adata-and-crucial/4

    [​IMG]

    I'd take 40 GB 2400 MHz over 32 GB 2666 MHz any day. 40 GB is 25% more RAM than 32 GB.
     
  9. imac275 macrumors member

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    Mar 24, 2013
    #9
    Thanks for posting this. Could you link to the actual memory that you have installed?
     
  10. dannys1 thread starter macrumors 68020

    dannys1

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  11. imac275 macrumors member

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    #11
    Thanks, I'll take a look.

    I am buying the base 27" iMac which can only take 32GB max, so I was going to replace the original 8GB with 32GB anyway. If this is cheaper and even slightly faster then it sounds like a great option.
     
  12. EugW macrumors 68000

    EugW

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    #12
    The base 2017 27" iMac can take up to 64 GB actually, even though Apple doesn't say that.
     
  13. dannys1 thread starter macrumors 68020

    dannys1

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    #13
    Apple does say that - you've been able to order 64gb iMac since the refresh.

    Its the 2015 that could take 64gb of Ram without Apple stating (though OWC said you needed to use a lower clock speed, not sure if that was actually true)

    If you're looking at a 2015 it won't run on 2666mhz ram and uses a different pin layout anyway (plus its DDR3L not DDR4)

    Edit: Sorry I presume you mean here that if you order the lowest spec iMac on the store it doesn't give you a 64gb drop down menu?

    In which case yeah - its the same iMac no matter what spec you order, they all run the same logic board and take the same Ram.
     
  14. imac275 macrumors member

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    #14
    Thanks. I guess they just say that because they only offer 32GB as an upgrade for BTO. I think 32GB will be more than enough for me anyway.
     
  15. EugW macrumors 68000

    EugW

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    #15
    Not for the base model 2017 27". It's only up to 32 GB. It's listed right in Apple's iMac Tech Specs as configurable only to 32 GB max. But 64 GB works just fine.
     
  16. ka111n macrumors newbie

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  17. dannys1 thread starter macrumors 68020

    dannys1

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    #17
    Well obviously 2666...

    But as EugW shows, unlikely to really notice in real life (You can't really tell the difference between the DDR3L and DDR4 in all honesty)
     
  18. kingdavidd macrumors newbie

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    Jun 22, 2017
    #18
    can you have a mix of 2400 and 2666? for example, first is stock apple memory @ 2400, and second paid is 32gb @2666?
     
  19. Trebuin, Aug 15, 2017
    Last edited: Aug 15, 2017

    Trebuin macrumors 65816

    Trebuin

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    #19
    Maybe, it depends on the design, but something is going to downclock.
    --- Post Merged, Aug 15, 2017 ---
    There's a formula that calculates CL vs the 2400/2666 speeds. Don't quote me on it, but I think it's the freq/CL value. the higher the number, the faster the ram. I'll have to do some digging again to verify it.

    Edit:
    (CL/(freq-in-MHZ) * 1000) = timing in ns
    Lower is faster
    https://superuser.com/questions/593772/calculate-performance-of-ram-using-timing-and-speed
     
  20. dannys1 thread starter macrumors 68020

    dannys1

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    #20
    Just wanted to clarify that you meant lower CL is faster there, not lower clock speed in case someone was confused.

    Probably also worth pointing out I did some tests on the 2017 iMac with the fastest (lowest) CL's it would take and some budget ram with higher CLs and it performed exactly the same on all RAM benchmarks so it appears to configure the timings the regardless of what CL you use.

    I haven't run any ram tests with 2666mhz ram yet though, but i'm due to get some more tomorrow so I will then and post the results in this thread. I'll also test with the stock ram as well and see if it boots and if so if it down clocks the 2666.

    Macs are certainly a lot more flexible than they used to be with what ram you can put in them (shame it's only the 27" iMac we can put stuff into though)
     
  21. Trebuin macrumors 65816

    Trebuin

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    #21
    Correct on lower CL is faster and higher frequency is faster, then the lower of the calculation should be faster:
    (CL/(freq-in-MHZ) * 1000) = timing in ns
     
  22. neko77 macrumors newbie

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    Zaragoza, Spain
    #22
    I've been reading about the RAM for this new iMac and I finally opted for HyperX 2400 (amazon.de).

    The memory timings for HyperX 2666 are 15-17-17 and for HyperX 2400 are 14-14-14.

    If we only compare CL it will be a win for the 2666 module (3,67 % faster). But how the other parameters affect speed? I have read formulas that combines all of them, in this case de 2400 module will be faster.
     
  23. stassk8 macrumors newbie

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    Feb 26, 2014
    #23
    Corsair Vengeance 16GB DDR4 SO-DIMM 3000MHz (PC4-24000) will work?
     
  24. princeking macrumors newbie

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    Oct 18, 2017
    #24
    interesting as I was just wondering if anything above 2400mhz would work and it does. would mixing the original 8gb 2400 with an additional 32gb 2666 work?

    I've been waiting to upgrade my ram and just been confused because of compatibly but as it seems any 260 pin would work right.
     
  25. redheeler macrumors 603

    redheeler

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    Oct 17, 2014
    #25
    Good to know. I've been running 32 GB of 2133 MHz DDR3 in my Late 2015 iMac and it also runs at native speed, works just fine. Just another reason I'm glad the 27" iMac still has upgradable RAM, and wish Apple would release a new Mac mini with it as well.
    I don't recommend mixing, and all of it runs at the lower speed (2400 MHz).
     

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