RAM power use question

[charlieiii]

I've started research for the next laptop which will be a sandy machine for general use with win7. I'll probably finally make the move to 64bit. RAM is is cheap enough so there's a temptation to install 8GB instead of 4GB. Since this is for a laptop power consumption matters. Does anyone know the impact on power consumption of adding a lot of extra RAM?

Does unused RAM on a system use significant power or does it only matter when the RAM is actually being used? (Or may be extra RAM is a waste until I have specific applications designed to use it?)

Finally, there are a lot of choices of RAM with different performance. Where can I learn the tradeoffs so I'm installing the right RAM for my situation?

Any guidance on this would be appreciated.

 

[VirtualLarry]

Well, having more RAM, does take more power, all of the time. But it also allows you to cache more data in RAM, rather than hitting the HD all the time, and the HD takes more power than the RAM does. So overall, I would generally say it's a win.

 

[charlieiii]

Well, having more RAM, does take more power, all of the time. But it also allows you to cache more data in RAM, rather than hitting the HD all the time, and the HD takes more power than the RAM does. So overall, I would generally say it's a win.

So the question is, how much ram is worth the extra heat and power? I'm sure most of my applications run only 32bit. Is 4GB the most sensible amount, 8GB, or 16? Regardless of cost when does memory become counter productive? I doubt that more is always better. It would be dumb to overload the machine with RAM that doesn't improve performance but does drain the battery a lot faster.

 

[fffblackmage]

If cost didn't matter, I would get 8GB. I don't think RAM consumes enough power to worry.

If battery life is so important, the cpu, gpu and display are much more significant factors to consider.

 

[Soulkeeper]

I know some of the xeon chipset manage to use power saving for unused memory (possibly other server setups too), but the desktops don't as far as I know.
DDR3 supposedly uses 30% less power than DDR2, but according to tomshardware guide the low voltage DDR3 saves only a few watts over regular stuff voltage:
"Peak power decreases from 178 W and 180 W at 1.5 V (DDR3-1333 and -1600 speeds) to 174 W and 177 W at 1.25 V and 1.35 V."
^^ total system wattage with 2x2GB ddr3

It would make a noticeable amount if you have a lot of memory I suppose ie: 16GB or more

 

[Soulkeeper]

Nice read on ram power usage

 

[charlieiii]

Nice read on ram power usage

Thanks. There is 2GB of RAM in my Latitude. Going to 4 times more has to be a hit on the battery unless the new RAM is significantly more energy efficient. Computers are getting more powerful, batteries aren't.