29. October 2023 · Categories: General

I was surprised to be reminded how much power RAM can consume in a laptop or NAS. NAS typically use slightly older technology, for example the Sinology NAS can be expanded with dual rank DDR4 laptop modules. I found a Micron technical note giving a deep dive. From page 24 there is an example for a 4GB configuration, where they calculate 1.6W typical draw, of which 350mW is background power. The other state is self refresh, which on a 1GB module is 25mA + 5mA @1.2V (Page 324). This gives the following estimates for DDR4 power consumption, scaled to 16GB:

State Power
Used 6.4W
Unused 1.4W
Standby 0.6W

These are rough estimates, given that multiple modules on the same bus add additional parasitic draws.

As such, you should aim for 50% utilization under load. Less, and you pay quite a bit in power for unused capacity, more, and your risk of needing paging increases, which will consume more power than unused RAM would, and drastically reduces performance.