K9UHGY8U7A is the same 25nm MLC NAND as in the Samsung 830.
As others noted, the controller is also identical to the 830 (The MCX). Not a newer revision.
Samsung new NAND in the 840 is 21nm. There is no such thing as 20nm NAND from Samsung.
The 21nm MLC is K9HFGY8U5A
and the TLC is K9CFGY8U5A
Just want to avoid spreading wrong information