Notebook Battery Life
I take a different approach to testing SSD power consumption. As end users, we never just read data or write data to our drives. Even if we did, power consumption varies based on the workload we apply. After a write takes place, the SSD consumes additional power to execute background tasks like garbage collection, TRIM and wear leveling. An SSD that consumes X watts while processing sequential data, Y watts processing random data and Z watts at idle might not facilitate better notebook battery life compared to another product found to use more power in those same tasks. Rather than looking at numbers of nearly insignificant value, we want to present the big picture.
There's a fourth drive in the above chart to help us make our point. With the SATA-based MyDigitalSSD SBe 120GB included, we see that there isn't a battery life advantage to using PCIe or SATA at this time. In fact, the SATA drive technically outperforms the three PCIe-based devices.
Samsung's SM951 delivers slightly more longevity than the older XP941. And both Samsung SSDs outshine Plextor's M6e Black Edition 512GB. With that said, Plextor sells the M6e Black Edition in a M.2-to-PCIe adapter, so it's not optimized for notebook use.
When you pull the power plug on your notebook, Windows changes power schemes to reduce power consumption. The CPU, memory, DMI, SATA and PCIe buses slow down in response. In some systems, the cooling fans are even spun down.
Naturally, in this state, performance is reduced. With that in mind, we can still measure SSD efficiency in a low-power environment. The rating we're reporting covers the entire platform. But the only variable changing between tests is the SSD. Samsung's SM951 and XP941 drives deliver the highest performance ratings in this power state.