[Tomchu]

I recently bought a 12" iBook, and it's a totally sweet little machine. I love the 5-hour battery life with WiFi on. Sometimes I manage to get ~6 hours if all I'm doing is writing. I've been thinking about adding another 512 MB SODIMM to bring my total memory up to 1 GB, but I'm not sure what kind of effect that would have on my battery life.

Given the specifications written on the bottom of the iBook battery, and given my average 5.5 hours battery life, I can more or less calculate the power draw in watts of my iBook. I can't find any specifications online for the power draw of a single 512 MB PC2700 DDR SODIMM. Does anyone have any experience with DDR RAM upgrades and the effect they have on battery life?

[DKeithA]

I have 1.5GB of DDR in my 12". I get at least 5 hours of battery life.

[cmeisenzahl]

I would expect the increase in power use to be negligible.

Chris

[mduell]

According to Samsung, it's 0.5-1W per 512MB.
If you're really getting 6 hours (which I find surprising) off your 50Whr battery, you're drawing 8.33W. Add two thirds of a watt and you're at 9W, giving you 5.5 hours of battery life.
So you lose half an hour of battery life.

[ghporter]

Increasing RAM should DECREASE the power used by your hard drive because the OS won't have to swap data out to the disk as much. Overall that should DECREASE your power consumption and INCREASE BATTERY LIFE.

[mduell]

Originally Posted by ghporter

Increasing RAM should DECREASE the power used by your hard drive because the OS won't have to swap data out to the disk as much. Overall that should DECREASE your power consumption and INCREASE BATTERY LIFE.

Doubtful. The difference between an idle hard drive and a reading/writing hard drive is only about twice the power consumption of having an extra 512MB RAM.
Unless you're spending half of your battery life swapping (ouch), adding the RAM will give you shorter battery life.

[ghettochild]

Originally Posted by DKeithA

I have 1.5GB of DDR in my 12". I get at least 5 hours of battery life.

same specs here. I get about 5h w/ wifi on/BT off and screen dimmed.

[frdmfghtr]

I also just got a 12" iBook, and dropped in a 512MB dimm this evening after running around on the stock 512MB RAM. I ran XBattery for a while and didn't see a noticeable increase in battery current. I was pulling about 1000 mA, give or take a little here or there. Up to now, I was getting in the 4.5-5 hour range as well. Perhaps some long-term data collection is needed to get a good average current draw.

Now, I have this thought. In the interest of preserving power, is it possible that the power management setup would turn off the unused bank of RAM and only turn it on when it's needed? With the extra memory I saw little to no increase in current draw.

(BTW...960 mA the whole time I was posting this)

[Dork.]

Originally Posted by mduell

Doubtful. The difference between an idle hard drive and a reading/writing hard drive is only about twice the power consumption of having an extra 512MB RAM.
Unless you're spending half of your battery life swapping (ouch), adding the RAM will give you shorter battery life.

I think that depends on what you mean by idle. You don't save much power if you're not reading from the HD but it is still spinning. However, if adding the RAM limits your hard drive accesses to the point where the drive can spin down and sleep, then you're talking some serious power savings.

[mduell]

Originally Posted by Dork.

I think that depends on what you mean by idle. You don't save much power if you're not reading from the HD but it is still spinning. However, if adding the RAM limits your hard drive accesses to the point where the drive can spin down and sleep, then you're talking some serious power savings.

The difference between reading or writing and idling is actually quite significant.

Below are the typical power figures for Hitachi's drives.
Startup (peak, max.) 5.5W
Seek 2.3W
Read (avg.) 2.0W
Write (avg.) 2.0W
Active idle (avg.) 1.1W
Low power idle (avg.) 0.85W
Standby (avg.) 0.2W
Sleep 0.1W

So the difference between idle/low idle and reading or writing is about 100%.
Spinning down is great, if you can buffer the right stuff in RAM... if you can't, the constant spin down/spin up draws a good bit of power and is hard on the drive's motor.

[Tomchu]

After getting a 512 MB SODIMM, I'm happy to report that my battery life is more or less the same as before (at most I'm seeing 5:30 instead of 5:40 under ideal conditions). In the long run I think this works out to a slightly better battery life because my hard drive won't be working as hard loading applications.

[accordracin96]

I have a iBook 14" and I recently upgraded the 512MB memory chip to 1GB.. I work at Best Buy, so i get a pretty good discount...

I do not notice ANY difference in battery life. At 98% battery, I get 4hrs 58 mins of battery life..

[mduell]

Originally Posted by accordracin96

I do not notice ANY difference in battery life. At 98% battery, I get 4hrs 58 mins of battery life..

Estimated, or did you time an actual discharge cycle?

[frdmfghtr]

Originally Posted by frdmfghtr

I also just got a 12" iBook, and dropped in a 512MB dimm this evening after running around on the stock 512MB RAM. I ran XBattery for a while and didn't see a noticeable increase in battery current. I was pulling about 1000 mA, give or take a little here or there. Up to now, I was getting in the 4.5-5 hour range as well. Perhaps some long-term data collection is needed to get a good average current draw.

(BTW...960 mA the whole time I was posting this)

A data point for those interested...

I kept data on the current draw with the 512MB DIMM installed, and the average current draw is about 1000mA. With the expansion removed, the average current draw seems to be in the area of 850-900mA with the occasional trip into the sub-800mA region. Assuming a 5V DIMM (is that right?) and about 100mA current draw, that come to 0.5W--about what somebody had posted earlier.

If XBattery saved the battery data as a text file of some sort, I could look at it better with a spreadsheet. However, I can't find where it saves (it has the option to save data, but no indication as to where and Spotlight didn't help since I didn't know what to look for).

As another data point for those still reading this post, my battery went from 4507 mAh capacity down to a current 4468 mAh after 25 cycles--about 2mAh per battery cycle. I wish my HP did that...I have one 4400 mAh battery down to 1800 mAh after only 130 cycles!

I guess we'll see if the trend continues...can you tell I'm slightly obsessed with battery life?

[MuyMalo1]

My G3 iBook is nearly 3 years old. Apple has had to replace the "video processor"???...
Screen freezes and eventually just stays black.

I've had to deal w/ this problems 5 times of which 3 were confirmed by a Mac Genius and eventually fixed at Apple's expense. What bothers me is that is has happened so many times around the fall season, almost clock accurate.

Apple is aware of the problem, because they posted it on their website, but will only fix it free up to three years from purchase and repair is guaranteed for 90 days; Meaning that if my iBook goes through this again next fall, I'll be on my own for something that they know is wrong.

I warned them that if this happens again, they MUST replace the machine w/ a new one OR refund what I paid according to a federal consumer protection law since there isn't a federal computer lemon law yet. Hope I never have to attack Apple, but eversince they fixed my iBook (2nd time), my battery lasts from 45-90 minutes at a 100% charge.

Hope no one has experienced this problems.

V.

[mduell]

Originally Posted by frdmfghtr

I kept data on the current draw with the 512MB DIMM installed, and the average current draw is about 1000mA. With the expansion removed, the average current draw seems to be in the area of 850-900mA with the occasional trip into the sub-800mA region. Assuming a 5V DIMM (is that right?) and about 100mA current draw, that come to 0.5W--about what somebody had posted earlier.

DDR2 runs at about 2.5V, but since you're measuring current from the battery (which is nominally 10.8V) 125mA would be 1.4W.

[frdmfghtr]

Originally Posted by mduell

DDR2 runs at about 2.5V, but since you're measuring current from the battery (which is nominally 10.8V) 125mA would be 1.4W.

Mmm, does that sound slightl;y high? I'll have to check the memory specs. It's a couple years old, so perhaps it's not as energy efficient as newer memory expansions?

[mduell]

Originally Posted by frdmfghtr

Mmm, does that sound slightl;y high? I'll have to check the memory specs. It's a couple years old, so perhaps it's not as energy efficient as newer memory expansions?

I've looked at white papers from a few other RAM companies and my original estimate (0.5-1W per 512MB) is on the low side. 1.4W is on the higher side of average, but not excessive.

[frdmfghtr]

OK I found the datasheet from ValueRAM for the memory module I have, and no wonder it made such a difference!

ValueRAM KVR266X64SC25/512 DDR266 memory module

Operating power: 2.9 W

I guess that would explain the noticeable power draw.

I treid to find the spec for Kingston's KTA-PBG4333/512 module which, according to their website, is the recommended 512 MB module, but I couldn't find a dataseet on it.

[mduell]

Originally Posted by frdmfghtr

OK I found the datasheet from ValueRAM for the memory module I have, and no wonder it made such a difference!

ValueRAM KVR266X64SC25/512 DDR266 memory module

Operating power: 2.9 W

I guess that would explain the noticeable power draw.

I treid to find the spec for Kingston's KTA-PBG4333/512 module which, according to their website, is the recommended 512 MB module, but I couldn't find a dataseet on it.

Is that for a laptop SODIMM or a desktop DIMM? That would be unreasonably high for a laptop SODIMM.

[Tomchu]

iBooks take DDR1, not DDR2.

[ghporter]

Originally Posted by Tomchu

iBooks take DDR1, not DDR2.

Laptop DDR1 typically runs at 2.5V as well.

[frdmfghtr]

Originally Posted by mduell

Is that for a laptop SODIMM or a desktop DIMM? That would be unreasonably high for a laptop SODIMM.

Laptop...that particular module is the one I pulled out of my HP laptop and used in the iBook for a while. Like I said, it's about 2-3 years old, so perhaps the apparent lack of efficiency is due to the age of the technology (spoken by a nonexpert mind you.)

[mduell]

Originally Posted by Tomchu

iBooks take DDR1, not DDR2.

Yes, and DDR2 would run at 1.8V instead of 2.5V.