Thinkpads Forum

Hi guys,
I already knew that adding more RAM will improve performance and reduce disk activities, especially on system with low RAM.
However, I couldn't find any information about the adverse effect of adding more RAM to battery life. I mainly prioritize battery life on an X rather than performance. But if there is no effect on battery life, a little more performance wouldn't hurt.
Any insight is much appreciated.

Adding more memory contributes in prolonging the battery life of a machine. I don't believe memory consumes alot of power from the battery, infact what it does is decreases the number of times your HDD gets accessed by your machine which consumes alot more power.

Thanks for the reply,
One thing I am specifically looking for is the data comparing the power consumption between different brands.
I am under the impression that not all RAMs from different brands have the same power consumption.

About the only way I know of determining which module draws the least amount of power is to consult the datasheets. However, they can be hard to find sometimes and they don't always spec the measurements in an identical manner. It's somewhat true that memory consumes less power than a disk drive. But here's some numbers from each company's respective datasheets:

Micron MT16HTF12864HY-667 (1GB DDR2 SDRAM PC2-5300):
Operating Burst Write current: 1416mA (that's 1.4 amps)
Operating Burst Read current: 1496mA (almost 1.5 amps)
Precharge Power Down current: 112mA

Hitachi 7K100 100GB Disk Drive (HTS721010G9AT00):
Power consumption Read (avg.): 2.0W (@5V equals 400mA)
Power consumption Write (avg.): 2.0W (the same 400mA)
Active Idle (avg.): 1.1W (220mA)
Startup: 5.5W (or 1100mA or 1.1 amps)

Now, these current figures are maximums, which means that they operate at somewhat lower amounts. How much lower depends upon how each company decides to spec their products. Peak current draw for the memory is when it's reading or writing data. This usually occurs for a very brief amount of time as most people don't use their systems for extreme number-crunching.

Thank you for the data.
It is exactly what I am looking for.

I've monitored the current draw/battery life on my T42 with .5GB in 1 SODIMM and 2GB in 2 SODIMMS. The difference is only about 1%. In practice, I think the power draw from extra memory is negligible. It is the number of read and write operations that determine the power used.