Sakkura :
Both the GTX 650 and the GTX 650 Ti have a 128-bit memory interface. The GTX 650 Ti Boost has a 192-bit memory interface, making it substantially better than the GTX 650 Ti.
None of these cards are 256-bit.
As I said I'm not sure about the exact model of Zotac, But It was a GTX 650 (I don't remember the index) with 1GB of GDDR5 ram, and I saw a bold and bright "256-Bit" labled on the box and the salesman emphasized on it for a couple of times.
If it's a real 256-Bit, do you think it's better than the Asus GTX 650 TI Boost 192-Bit?