RAM vs Energy

[SteveCo]

Hi

Does increased GB of RAM increase power usage if one is using the same number of DIMMS? e.g., on a new rMBP, if you spec 8GB I think you get 2 x 4GB, if you spec 16GB I think you get 2 x 8GB.

If so, has anyone found any data on the effect on battery life?

I've been looking all over but can't find anything.

Thanks

SteveCo

 

[ch33zw1z]

Not a significant amount. If you're measuring power, you won't even see a difference.

I went from 4GB to 8GB on a laptop, battery life not affected at all. Screen brightness and disk usage seem to be the big power draws.

 

[_Rick_]

Depending on your use, more RAM may decrease or increase overall power use -- but not by any noticeable amount. Even RAM voltage has little impact, unless you start exceeding the 1.5V JEDEC - power scales to the square of the voltage, so 1.5-1.65 has a bigger difference inn power consumption than 1.35-1.5. Nonetheless, next to even the storage subsystem the consumption is quite low.

 

[SteveCo]

Thanks both.

My assumption is that I will not reduce use of the page file or make any incremental savings of energy by having more RAM (for example for less use of the page file) - in short because currently I have to push the system very hard indeed before the page file is used and, even then, it is absolutely tiny (a few mb). In fact, I suspect that for my use of the computer (DTP, minor photo editing, Logic Pro X for electronic music (not massive soundbanks) the processor (dual core i7) is going to fall over before I am able to make much use of more than 8gb RAM.

My concern really is to maximise battery life, but to future-proof as much as possible whilst at it!

 

[Kallogan]

At idle on a laptop, add barely 0,5W for the second memory stick. At full load, dual channel is definitely more power hungry, i got 64W watts 8GB single channel vs 72W for 16GB dual channel. Power at the wall from Asus N550JV. It's with DDR3L 1,35V.

So yeah if your laptop idles below 10W, even 0,5W starts to matter battery wise. But for most laptops, it's peanuts. And you will rarely run at full load on battery, but depends on your usage really.

 

[SteveCo]

At idle on a laptop, add barely 0,5W for the second memory stick. At full load, dual channel is definitely more power hungry, i got 64W watts 8GB single channel vs 72W for 16GB dual channel. Power at the wall from Asus N550JV. It's with DDR3L 1,35V.

So yeah if your laptop idles below 10W, even 0,5W starts to matter battery wise. But for most laptops, it's peanuts. And you will rarely run at full load on battery, but depends on your usage really.

Thanks Kallogan - the thing is, it's the same number of sticks, just they'd both be twice the size (2x8 instead of 2x4). I imagine that the increase in power draw is even less then.

Also, with Mavericks, the use of RAM seems relatively unrelated to load - it likes to cache files quite aggressively, using up available RAM even under very low-load conditions.

 

[VirtualLarry]

At idle on a laptop, add barely 0,5W for the second memory stick. At full load, dual channel is definitely more power hungry, i got 64W watts 8GB single channel vs 72W for 16GB dual channel. Power at the wall from Asus N550JV. It's with DDR3L 1,35V.

So yeah if your laptop idles below 10W, even 0,5W starts to matter battery wise. But for most laptops, it's peanuts. And you will rarely run at full load on battery, but depends on your usage really.

I would think that this increase in power, would be more than offset from the decrease in power used by the storage device, due to more caching.

 

[hackerballs]

you should not be using any of your page file EVER! (only for dump logs) With 8 gigs RAM you can turn it off if you like, 16 gigs for sure. A page file acts like RAM when all your RAM is used up. It will allocate a portion of your HDD to act as RAM. This is like pouring Molasses on a turntable! It will still work, BUT SLOW.

 

[wholesalestunna]

you should not be using any of your page file EVER! (only for dump logs) With 8 gigs RAM you can turn it off if you like, 16 gigs for sure. A page file acts like RAM when all your RAM is used up. It will allocate a portion of your HDD to act as RAM. This is like pouring Molasses on a turntable! It will still work, BUT SLOW.

How do you turn off the page file? Also, I've been using a CPU usage meter to monitor my CPU and RAM use and mine is being used, but I'm usually not even using 40% of my RAM.

 

[hackerballs]

left click my computer/properties/Advanced system settings/Performance settings/Virtual settings-change/

set it up here on drive C (I assume C) with no paging file ,0mb ,set. restart PC

 

[wholesalestunna]

left click my computer/properties/Advanced system settings/Performance settings/Virtual settings-change/

set it up here on drive C (I assume C) with no paging file ,0mb ,set. restart PC

Awesome... Never knew that was there. What would happen if you put it down to 0 and then you ran out of RAM? Just a really slow computer? Maybe a crash?

 

[bononos]

Awesome... Never knew that was there. What would happen if you put it down to 0 and then you ran out of RAM? Just a really slow computer? Maybe a crash?

I think thats what would happen. I would leave the default settings as it was, theres no benefit to disabling paging.

 

[SteveCo]

you should not be using any of your page file EVER! (only for dump logs) With 8 gigs RAM you can turn it off if you like, 16 gigs for sure. A page file acts like RAM when all your RAM is used up. It will allocate a portion of your HDD to act as RAM. This is like pouring Molasses on a turntable! It will still work, BUT SLOW.

This is on OS X

 

[SteveCo]

I would think that this increase in power, would be more than offset from the decrease in power used by the storage device, due to more caching.

That's my fear!

 

[_Rick_]

Awesome... Never knew that was there. What would happen if you put it down to 0 and then you ran out of RAM? Just a really slow computer? Maybe a crash?

Any application requesting memory when the system is oom will be killed. If it's the kernel/system requesting more memory, I'm not sure if it just kills a random userland app, or if the entire system goes down.

Disabling the page file is trading potential data loss against some minor storage space.

 

[john3850]

If I use sleep mode with no pagefile how does your dirty memory get refreshed.
I also use a 4GB fast ram page with no pagefile how does your dirty memory get refreshed without a page.
I run a small page on the system ssd so it can write the errors if needed.

 

[hackerballs]

It would be asking too much that everyone understands what the Page file does in the first place. If you were to ever need it, 40 times slower than using just the RAM. It's just VIRTUAL RAM, (means not really real Ram).
Today if your PC went into page file to render anything, you should just give up. Buy a new PC with enough RAM. Sad PC that will use page files for RAM.

Page file is a throwback to when no one had enough RAM. nowadays, not needed. Test it yourself and see if you need more RAM. Doubt it if you have 8 gigs, not even close with 16 gigs. Like I said, only needed if you need to write errors/dump files. Refreshing everything is just restarting your PC. This cleans most registry errors (which are mostly web sites you are no longer on)(do not buy a cleaner)

And your PC would just stop if it had to use page file with it shut off. When you freed up RAM it would be fine. Please don't be cheap and just have 2gigs RAM in your PC. Today RAM is very cheap.

And another reason is that your boot times will speed up and so will switching between apps.

and YES, you can leave it on if you like, it's just a small tweak in the first place, but that's what it's all about, SPEED, isn't it?

have a great day

 

[VirtualLarry]

It would be asking too much that everyone understands what the Page file does in the first place. If you were to ever need it, 40 times slower than using just the RAM. It's just VIRTUAL RAM, (means not really real Ram).
Today if your PC went into page file to render anything, you should just give up. Buy a new PC with enough RAM. Sad PC that will use page files for RAM.

Page file is a throwback to when no one had enough RAM. nowadays, not needed. Test it yourself and see if you need more RAM. Doubt it if you have 8 gigs, not even close with 16 gigs. Like I said, only needed if you need to write errors/dump files. Refreshing everything is just restarting your PC. This cleans most registry errors (which are mostly web sites you are no longer on)(do not buy a cleaner)

And your PC would just stop if it had to use page file with it shut off. When you freed up RAM it would be fine. Please don't be cheap and just have 2gigs RAM in your PC. Today RAM is very cheap.

And another reason is that your boot times will speed up and so will switching between apps.

and YES, you can leave it on if you like, it's just a small tweak in the first place, but that's what it's all about, SPEED, isn't it?

have a great day

You are completely and utterly wrong. A pagefile is a performance optimization for modern VM-based OSes. It frees up RAM for usage by the current foreground app's working-set, or for file-caching. If stale pages weren't evicted into the pagefile, you would have far less RAM available for your current foreground app to run in or cache files with, and it would slow down.

Edit: The worst-case scenario changes a bit though, between having a pagefile and not. If the system runs out of RAM, without a pagefile, the kernel has no choice but to start randomly killing user-mode processes. With a pagefile, it may start "thrashing" the pagefile. It's a tradeoff between responsiveness and lower user latency, versus availability of the OS. Neither situation is ideal, so a RAM upgrade at that point is essential.

 

[Ovven]

I've been running with no page file since winxp days. In WinXP you'd sometimes get an error or two in a period of a year, but for win7 I had never had that happen. The only program that would ever bitch about missing pagefile was older versions of photoshop, and even that stopped with the never versions.