[sf-lug] will increasing RAM increase power draw during suspend-to-RAM?

John Magolske b79net at gmail.com
Thu Sep 4 13:25:20 PDT 2008

* Alden Meneses <aldenm at gmail.com> [080904 11:42]:
> On 9/4/08, Mark K. Zanfardino <mzanfardino at gmail.com> wrote:
> > John Magolske wrote:
> > > When suspended to RAM, a laptop's battery is slowly drained. My
> > > understanding is that this power is going towards keeping the
> > > RAM active. I'm wondering how much of the total power draw is is
> > > being consumed by the RAM chips. Would doubling the amount of
> > > RAM from say 512MB to 1GB have the effect of roughly doubling
> > > the power consumption while suspended?
> >
> > This is a very good question and it brought to mind the fact that
> > my laptop does not maintain it's battery life nearly as long as
> > it had prior to my adding an addition 1GB SODIMM to the existing
> > 512MB base RAM installed. Prior to the expansion I could safely
> > leave my laptop in sleep mode for nearly 24 hours; now it doesn't
> > last 12. I haven't run any conclusive tests to see how long it
> > will last, but clearly there has been a dramatic decrease.

That's the situation I'm looking at on my ThinkPad X40 -- 512MB RAM
soldered in place and an empty SODIMM slot. Generally I run text-mode
in a framebuffer console, so memory usage rarely exceeds 100MB. I'm
reluctant to add RAM if it's going to substantially reduce battery
life while suspended.

It would be handy however to have more RAM while using Iceweasel
with lots of tabs open, or running some occasional memory intensive
process. I wonder if there's a way to have an additional 1GB SODIMM
lie dormant, drawing no power, and turn it on as needed. Even doing so
manually would be ok, some sort of 'swapon' equivalent... possible?

> Could it be other factors like the age of the battery? I have not
> changed anything on my laptop in regards to the hardware and the
> battery life is not what it used to be.

Aging batteries will gradually loose their capacity to hold a charge,
but if I understand Mark's situation, there was a more abrupt change.


John Magolske

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