- DDR - Double data rate (...Nth generation synchronous dynamic random-access memory)
- LPDDR - Low Power DDR
- DDRL - DDR Low Voltage
Image from https://blogs.synopsys.com/committedtomemory/2014/01/10/when-is-lpddr3-not-lpddr3-when-its-ddr3l/
- DDR4 is 1.2 -1.4v
- DDR3 vs DDR4 (no performance difference in practice, the most important are memory latencies and frequency)
- LPDDR4 is not there yet (Intel CPUs does not support it, it is planned in Cannonlake 2018)
- LPDDR3 (e.g. Macbook Pro 15'' 2016 16GB RAM 76Wh), regular load
1.49A x 1.2V = 1.79W
- DDR4
"The power consumption difference between the system equipped with low-voltage and regular memory is only 2 W in idle mode and about 3 W under load." – http://www.xbitlabs.com/articles/memory/display/kingston-lovo-hyperx_3.html#sect1
It's impossible to get an exact figure on it, but depending on the usage it can be estimated that between 2 and 5 watts are saved using LPDDR3E RAM instead of DDR4. And since the system averages to drawing about 20 watts on battery in normal usage, this can be said to be the difference of the RAM using 2 watts versus 3-6 watts for DDR4. Translated to overall power usage that would make the difference of 10% of power being dedicated to RAM versus the 20-30% it would be for DDR4.
Example usage of 7 hours (very approximate calculation):
- LPDDR3 1.79W x 7h = 12.53 Wh (~16.5% of battery capacity)
- DDR4 3.79W x 7h = 26.53 Wh (~35% of battery capactiy)
