> power losses are going to be small compared to the rest of the stack
While certainly not the largest losses, they do not appear insignificant. In LPDDDR4 they introduced[1] a new low-voltage signalling, which I doubt they could have gotten working with SODIMMs due to the extra parasitics.
If you look at this[2] presentation you can see that at 3200MHz a DDR4 SODIMM would consume around 2 x 16 x 4 x 6.5mW x 3.2GHz = 2.6W for signalling going full tilt. Thanks to the new signalling LPDDR4 reduces this by 40% to around 1.6W.
Compare that to a low-power CPU having a TDP of 10W or less a full 1W reduction per SODIMM just due to signalling isn't insignificant.
To further put it into perspective, the recent Lenovo ThinkPad X1[3] uses around 4.15W average during normal usage, and that includes the screen.
Obviously the memory isn't going full tilt at normal load, but say average 0.25W x 2 sticks would reduce the X1's battery lifetime by 10%.
edit: yes I'm aware the presentation is about LPDDR4 yet the X1 uses LPDDR5, just trying add context using available sources.
And this line of thinking is exactly why we can't have M1 Macbook levels of battery life on Windows laptops. Believe it or not but a lot of people like to be able to have a light device they can just take without a charger and use for a solid day or 2 of work.
While certainly not the largest losses, they do not appear insignificant. In LPDDDR4 they introduced[1] a new low-voltage signalling, which I doubt they could have gotten working with SODIMMs due to the extra parasitics.
If you look at this[2] presentation you can see that at 3200MHz a DDR4 SODIMM would consume around 2 x 16 x 4 x 6.5mW x 3.2GHz = 2.6W for signalling going full tilt. Thanks to the new signalling LPDDR4 reduces this by 40% to around 1.6W.
Compare that to a low-power CPU having a TDP of 10W or less a full 1W reduction per SODIMM just due to signalling isn't insignificant.
To further put it into perspective, the recent Lenovo ThinkPad X1[3] uses around 4.15W average during normal usage, and that includes the screen.
Obviously the memory isn't going full tilt at normal load, but say average 0.25W x 2 sticks would reduce the X1's battery lifetime by 10%.
edit: yes I'm aware the presentation is about LPDDR4 yet the X1 uses LPDDR5, just trying add context using available sources.
[1]: https://www.jedec.org/news/pressreleases/jedec-releases-lpdd...
[2]: https://www.jedec.org/sites/default/files/JY_Choi_Mobile_For...
[3]: https://www.tomshardware.com/reviews/lenovo-thinkpad-x1-carb...