The NP900X3A did actually have two SODIMM slots as John mentioned whereas this one, the NP900X3B does not.
I think the comment should say: "Our original statement about user-removable RAM is incorrect. The 900X3B includes 4GB of fixed RAM, UNlike its predecessor. Thanks to our readers who have caught this error."
I was intrigued that the surface temperatures observed are significantly higher than my own measurements (41C maximum at the bottom back and 39C on the keyboard). A look inside revealed two fans both serving the CPU, which explains why my NP900X3B stays cool and quiet under load. However, my RAM is soldered on the board because the twin fans leaves no space for any SODIMM slots.The 15" NP900X4B, however, has a single fan and a pair of SODIMM slots.
Great review, covers every aspect of this notebook/ultrabook. One thing I wanted to clarify: You mentioned in bold that the memory is not soldered on, how did you confirm this? Did did you open up the whole bottom shell to verify? Because based on my disassembly of this notebook, I found that the memory chips are actually soldered on the motherboard, so there's no way to upgrade or change the memory. Here is a short video clip I took of the disassembled NP900X3B, and you can see the memory chips has a silver metal plate protecting it, located just beneath the two black heatpipes in the middle. I believe there is no way to take out the memory, unless somehow there are different revisions of the same model:
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