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How much is the battery life reduced by increasing RAM?

Logic would dictate that increasing the RAM in any Laptop would decrease the battery life. But by how much? If I have a machine with 2 GB and can take it to 8 GB should I? So what is the effect of moving a machine from 2 to 4, 2 to 8 or on the newer machines to 16 GB of RAM? Is there any real research on this or just old wives tales?

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The age of the memory modules is a bigger factor. Newer denser modules use less power than older units of the same size.

Even still more modules will use more power so if the system can support a denser module use it so using two 1GB modules uses more power than one 2GB module (total of 2GB). Or, using two 2GB uses more than one 4GB module (total of 4GB). When you get to 8GB or 16GB setups you may not be able to use a single module as the firmware of the given system may not be able to handle it (or have the needed address lines).

Just like baking a cake you can over do one ingredient making a messy cake ;-} The balance of the different ingredients is what makes a great cake.

I agree with Cernestean Ciprian HD storage uses more power within the system. While using a SSD can reduce the power usage the issue of price and space then becomes a factor. This is where a hybrid drive can help. It still has its limits, depending on the applications being used.

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Dan are you trying to say that adding memory, especially older memory will decrease battery life???? Furthermore are you implying with your "messy cake" that one can have too much RAM in their system and it will eat up battery life??? Somehow adding a faster hard drive before maxing out RAM is a wise decision and will save battery life???? LMAO


If you limit the question to just memory then older RAM modules are less efficient than newer RAM modules. That is why I also pointed to the whole system as needing to be reviewed.

If you are talking about the complete system then the HD is the bigger burner of power. This is were the type and size of drive can improve things a SSD is a very good start but even its size can effect things. A SSD which is on the small size may not have enough free space causing the system to work harder (and wear out) the SSD.


This also gets tricky as it also depends on what you are doing. Simple surfing tends not to be a big CPU, RAM or storage user. But, heavy gaming or graphics can consume much more power as all three elements of the system will be more involved. The level of processing the CPU is doing. The range and depth of the image the GPU is displaying being the biggest users. Virtual RAM & Paging is then dependent on how much RAM is present in the system which then drives the SSD/HD harder. And last, what is stored on the SSD/HD that is needed (used) by the given app.


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True, but different components drain different amounts of power from the battery.

Memory is a negligible factor, because it uses very little power (we're talking less than 3 watts per stick in a laptop).

And in fact, if you have a HDD, more memory usage would theoretically increase battery performance, because there is less HDD activity when memory is used as cache, instead.

The most power hungry components are ones that generate heat (CPU and GPU as they process information) and those that generate physical motion (the fans and any hard drives). Memory tends to generate relatively little heat (and obviously no physical motion).

The first steps I would take in increasing battery consumption would be to replace the HDD with an SSD, get a new battery and maybe replace the fans with those of better quality (harder to do on a laptop). Also abstain from any GPU or CPU intensive tasks. Any efforts beyond that are adding immeasurably small amounts of battery life.

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My question would, since we are talking about battery consumption, is how do you determine how much wattage the battery will provide, how much is being used during different operations and over what period of time.


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You're talking about "paging", a common technique that Windows or OS X use to allow you to run big programs or work on large files (e.g. video editing) that takes more storage memory space than you have installed in RAM. Installing more memory will decrease the amount of paging, so decreasing the amount of HDD activity, and draining much less of your battery power. Reading and writing to HDD involved mechanical spinning a stack of multiple ceramic/metallic disks and moving the read/write heads back-and-forth. Easy to appreciate this takes much more power than reading and writing to memory (more like reading/writing to a USB key). Here are the things to try, as needed, in the order listed to improve your MBP's speed when browsing:

1. In Safari Preferences/General, reduce the History item retention to only as long as you need to. If you use Add Bookmark and Add to Reading List for stuff you want to revisit later, you don't need to keep your browsing history for long. Set "Remove download list item" to "Upon successful download" or any other seeing but never Manual to remove junk within a day. Along this line, I run the free version of CCleaner every time I'm done with browsing for 2+ hours on my old MBP.

2. If you're using OS X Yosemite or earlier, boot to Recovery Partition (press and hold down Command and R) after hearing the beep on a Restart) and use Disk Utility to Repair Permission. I find benefits in doing this monthly on my 2008 MBP running Yosemite. I also run off ethernet from my router rather than Wifi when browsing heavily.

3. Maximize the amount of memory on your MBP. If you have a Late 2007 MBP, you can upgrade it to 6GB with an upgrade kit from OtherWorld Computing

4. You'll see an immediate speed benefit on system boot after upgrade to SSD drive. After that, human think-time and network bandwidth is the overwhelming factor when browsing.

I successfully upgraded my Early 2008 MBP to 6GB ram with this kit before I install OS X Mavericks. I currently have OS X Yosemite installed on this Mac and is still happy with it. My HDD is only a 5400rpm drive. I found it overheated with a 7200 rpm HDD and ruined a new battery within 4-6 months.

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Paging and Virtual RAM are different but both leverage the hard drives space. So simply put, more memory uses less of either.

Virtual RAM: Uses the CPU's address lines to extend the RAM space into areas on your hard drive (HD) or solid state storage (SSD).

Paging: Is a technique apps use to move parts of the file you are working on when the file is very large on to your hard drive (HD) or solid state storage (SSD). As an example gaming a a very big user of Paging.

It's not uncommon for people to mix up the two. And in truth it really doesn't matter which is being used. OS's use V-RAM, Apps us both V-RAM and Paging (if programed to do so).


Thanks for describing Virtual RAM. The last time I use that was either running DOS or Windows 3.1 or 3.5, using 3rd party apps. Around when Windows started supported 32-bit addressing, I forgot all about virtual ram because it offered nothing the OS doesn't already provide. I had no idea the OS developers used V-RAMs under the cover. Then again, I wasn't in that business. Thanks for the tidbit.


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This seems old, but I wanted to ask about it. If the laptop (Macbook Pro 2007) is running 2GB of RAM and slows down and also uses HDD to buffer because it is running out of RAM, would increasing physical RAM not reduce the search times and the need to use the HDD?

I am considering also installing a SSD in the future and have read that the battery life would not improve much.

My main concern is my battery (new recently) lasts less than an hour when I am browsing and it doesn't matter whether it is WiFi or ethernet connected. At some point it starts to drag and when I check the Activity Monitor the RAM is almost gone and the battery seems to take a dive.

Update (04/05/2016)

Hi Mayer,

Sorry for the delay in the reply, but I finally made it down to the parts store to buy RAM and it turned out to be wrong. I had to wait another 3 weeks to get back down and get the correct sticks. I put in another 2 GB to up it to 4 GB total...seems to run much better.

It has 70GB of the 120GB drive. and most of that is OS files. This was a gift from a friend/customer that I did some work for and I never really bothered too much with it until my Windows box crashed (monitor, actually). I also got that sorted out with a new monitor and now I use the old one with the Macbook using the DVI port. The VGA port was toast on the monitor but the DVI works fine.

Anyway, I can look at posting a proper question but thanks for the answer.

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@marky9989 How much hard drive space (as a percentage) do you have left on your HD?

This really needs to be a new question to get the proper attention.


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mayer will be eternally grateful.
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