11-18-2016 01:47 AM - edited 11-18-2016 01:49 AM
I installed ADATA SX900 (512GB) SSD for my X201 Tablet, which is SATA3.
According to the hardware specs, X201 supports dual drives via its SATA3 and mSATA interface. If you're considering to use PCIe, make sure it's mini PCIe. Another thing is to ensure you've no WWAN (3G WAN) installed, because WWAN occupies the mSATA/mPCIe slot.