Does anyone have the specs on the ADATA XM11 solid state drive that's in some of the new Zenbooks?

It's meant to be a 128GB disk, but mine's only reading as 120GB. (114472MB to be precise.)

3 Answers 3


Apparently, the ADATA XM11 is actually only 120GB in capacity.

The SSD Review did a teardown to compare the two SSDs used in the ASUS UX21 and UX31 Zenbooks, and mention that ASUS somewhat deceitfully markets both as being 128GB. While the Sandisk U100 SSD certainly is, the ADATA XM11 is not.


Modern SSDs always have over-provisioning which is where the other 8GB has gone.

Just as HDD manufacturers list their capacities in gigabytes instead of gibibytes, to maximize the numbers, some SSD manufacturers list the entire amount of NAND including what has been used for over-provisioning to make the capacity look larger.


Formatting the drive will result in some capacity being used by overhead functions. This often means formatted capacity is less than the "advertised" capacity. Also, many makes round out the size to a common size like 1 TB and convert based on 1000 megabytes is 1 gigabyte when in reality the conversion is 1024 megabytes to 1 gigabyte so for example, a 750GB hdd is really only about 732 GB.

  • You're thinking of a Gibibyte, 2^30 bytes*. However 114472 x 1024 x 1024 = 120 032 591 872 which is either 120GB or 111.8 Gi. Either way not 128. *I wish the IEC conventions were in more common use, it's been more than a decade and I'm still having conversations like this
    – Spike
    Jan 17, 2012 at 2:59

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