SSD + 1.35V Ram Power Savings?

Discussion in 'MacBook Pro' started by Titanium81, Nov 19, 2011.

  1. Titanium81 macrumors 6502a

    Titanium81

    Joined:
    Jun 23, 2011
    #1
    Would swapping the HDD for an SSD and adding 1.35V Ram on a 13" MBP conserve power (extend battery)?

    Has anyone done this? What type of battery life are you getting? 7+ hours?
     
  2. Mersailios, Nov 19, 2011
    Last edited: Nov 19, 2011

    Mersailios macrumors regular

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    Oct 23, 2011
    #2
    I'd also like to know if there is much of a difference between 1.35V and 1.5V DDR3 memory when it comes to battery life in a MacBook Pro out of curiosity...
     
  3. snaky69 macrumors 603

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    Mar 14, 2008
    #3
    An unbiased guesstimate: Roughly 5 to 10 minutes on a full charge, tops. RAM really isn't what's the most power hungry in a computer.
     
  4. pharonyk, Nov 19, 2011
    Last edited: Nov 19, 2011

    pharonyk macrumors member

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    Sep 13, 2009
    #4
    I've just purchased my first RAM upgrade for my 2011 MacBook Pro. It took me hours just to find the right information I was looking for...

    I hope this answers all your questions as it has done for me:

    http://forum.crucial.com/t5/Standar...-35v-1-5v-Dual-Voltage-DDR3-memory/ta-p/71731

    And yes, I've went with the 1.35V.

    Same performance -- More energy efficient. :)
     
  5. thundersteele macrumors 68030

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    Oct 19, 2011
    Location:
    Switzerland
    #5
    so, the MBP supports DDR3L then?

    @OP:

    It seems that SSDs do not have a notable impact on power consumption. The SSD guide says that user reports differ in whether SSDs reduce or increase power consumption.
     
  6. pharonyk macrumors member

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    Sep 13, 2009
    #6
    No, the MacBook Pro (Early/Late 2011) doesn't. That's different.
     
  7. dusk007, Nov 20, 2011
    Last edited: Nov 20, 2011

    dusk007 macrumors 68040

    dusk007

    Joined:
    Dec 5, 2009
    #7
    I also think this is an interesting topic so I did another google search.
    This IEEE paper was most interesting.
    An empirical study of performance and power scaling of low voltage DDR3
    This paper appears in: Electrical Performance of Electronic Packaging and Systems (EPEPS), 2010 IEEE 19th Conference on
    Issue Date: 25-27 Oct. 2010
    E-ISBN: 978-1-4244-6866-9

    As some of you probably have no IEEE access I will summ up the most important parts.
    The biggest power savings are actually not at the DRAM side (about 20%) but at the MCH (around 40%). Still it is not a whole lot when not active.
    DRAM+MCH / DDR3/DDRL/delta%
    avg power mW 690/450/21%
    self refresh mW 570/390/32%

    Under full load difference was about 4-5%, which is around a 2W saving of power with 45W load power consumption of the tested notebook. Not a whole lot but about as much as taking away the entire power consumption of an HDD or 3 idle sitting HDDs.

    Idle savings are much lower. 690-450 = 240mW. That is not very much with the idle power of a MBP it translates into about 10min more.
    With Standyby almost only the DRAM is still active and the lower refresh power translates into a much bigger saving.
    It was 1.3 vs 1.1 W with their notebook (7.5h added Standby). With MBPs low 0.6W or so it might be 0.4 W and yield you 30% longer standby time. That is just a guess though, one would need to check that out.

    There are more tables but I am not entirely sure what they mean. It seems as some show only the DDR active power consumption without the total system power. And they tested different configurations. In Short. DRAM seems to be responsible for about 5-8W of consumed power under load and 3.5 (ddr3l) and 4.4 (ddr3) under light load. They tested different vendor modules and 8/4 GB configs. Active power between 8 and 4 GB is only negligible difference. There is more difference between different vendors. MCH IO is 30% less power. Another 1.7-2.3W high workload.
    All in all it looks like the memory sub system is responsible for 7-10W of total system power under heavy load.

    In conclusio the difference is about as big as cutting away the HDD or SSD power consumption completely. It is not so much that it really justifies significantly higher prices but 5% here and 5% there helps in the end.
    Also keep in mind these numbers stay about the same so the benefit increases the less power a system needs. A netbook with an avg power of 4-5 W will benefit much more.

    No but they help by increasing the run to idle tremendously. Launching my Eclipse dev suite on an SSD is done in about 1/4 the time and it consumes the same amount of power. The system sucks say 20W for 4 seconds as opposed to 16 seconds. That makes quite a huge practical difference. Also app launch speeds are so quick that it is less inconvenient to shut down apps one is currently not using and cut down on power. I used to have stuff like Eclipse running always because it took so long to launch with an SSD I can shut down everything but the essentials and get 7h battery life in stead of 4.
    DRAM is still the same performance but with SSDs the speed helps a great deal.
     
  8. Titanium81 thread starter macrumors 6502a

    Titanium81

    Joined:
    Jun 23, 2011
    #8
    Thank you for all the posts. I think I will get the 1.35V Ram. Every little bit of power savings adds up. An SSD would be a nice upgrade too since the power savings comes from the quick run and return to idle times... maybe I will do that in a year when the price per GB comes down a bit.

    All in all thanks for all the great and very informative posts! :)
     
  9. thundersteele macrumors 68030

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    Switzerland
    #9
    Thanks dusk007 & pharonyk for great informative posts.

    I looked up the study. One thing that struck me is that the difference in power consumption between "vendor 1" and "vendor 2" is almost as large as the difference between 1.5v and 1.35v ram. Unfortunately there is no way to tell which brand "vendor 2" is.

    The savings in a realistic setting seem to be about 2% or 5-10 minutes, as already mentioned above.

    I wonder what happens if one just uses one memory bank. Of course that's bad for the system performance, but for an ultra-portable or netbook, it might make sense to only have one ram module. However those laptops often don't really have memory banks, so maybe this is a useless thought.

    Now I'm still confused as to whether the 2011 MBPs will run the memory in 1.35v mode, provided that the appropriate memory kit is used. Pharonyk seems to imply that this is indeed the case, but besides this post, this is not mentioned anywhere else.


    Btw, here's a SSD - HDD comparison that also looks at power consumption. Both types of storage have essentially zero energy consumption when idle, and very similar consumption when in use. Thus, as dusk007 already explained, the main advantage of the SSD is that it can spend more time in idle, since it is much faster. This does not apply if the duration of the process is limited by other factors, e.g. by download speeds from the internet.
    http://www.notebookcheck.net/SSD-versus-HDD-in-comparison.18750.0.html
     
  10. Titanium81 thread starter macrumors 6502a

    Titanium81

    Joined:
    Jun 23, 2011
    #10

    The last paragraph of the above link states:

    "In case you always want to have the latest firmware update on SSDs, you indeed have to often accept the deletion of all data on the SSD. This is currently a problem for use in laptops as the only system disk."

    Is this correct?
     
  11. thundersteele macrumors 68030

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    Switzerland
    #11
    Probably. In any case, I would make sure to have a recent backup before I start messing with the hard drive.
     
  12. dusk007 macrumors 68040

    dusk007

    Joined:
    Dec 5, 2009
    #12
    How often do you want to upgrade the firmware?
    Most people take it as it is or update it once they recieve it. If there are problems you might update the fw once during the whole time you have it.

    For the whole process it is the easiest. To put the whole drive into some running Desktop PC (of friends, parents whatever) and backup the contents of the drive on one big enough drive (usually hdds can save a full SSD easily). Update it savely and well use it as it is if everything went fine or transfer the data back if it is necessary.
    I do it this way because SATA - SATA is the quickest. Desktop HDDs can do 120 MB/s everything but USB 3 or thunderbolt is slower.
    For me that is always the easiest and savest route, but
    In theory many Windows update tools don't require to delete all data only recommend backing up. OSX support is missing for many such tools thus you might have to use Windows or a Windows PC.
     
  13. dusk007 macrumors 68040

    dusk007

    Joined:
    Dec 5, 2009
    #13
    How often do you want to upgrade the firmware?
    Most people take it as it is or update it once they recieve it. If there are problems you might update the fw once during the whole time you have it.

    For the whole process it is the easiest. To put the whole drive into some running Desktop PC (of friends, parents whatever) and backup the contents of the drive on one big enough drive (usually hdds can save a full SSD easily). Update it savely and well use it as it is if everything went fine or transfer the data back if it is necessary.
    I do it this way because SATA - SATA is the quickest. Desktop HDDs can do 120 MB/s everything but USB 3 or thunderbolt is slower.
    For me that is always the easiest and savest route, but
    In theory many Windows update tools don't require to delete all data only recommend backing up. OSX support is missing for many such tools thus you might have to use Windows or a Windows PC.

    Would probably save some energy. If the CPU only nees to drive one 64bit memory channel instead of two while the other does nothing it probably cuts down on load power consumption. Of course there is no different power states or power gating. Thus if one channel is not in use it doesn't take away all the power it usually consumes just less load power. I doubt it would be worth it.
    Most of the current gen mobile phone/touchpad SOCs support two 32bit channels but currently none afaik uses both. Yet they are probably power gated and not using them helps saving PCB costs too.
     

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