72Mbit QDR II — what the 400 MHz clock buys you
QDR II's separate read and write ports eliminate the bus-turnaround dead cycles that plague standard synchronous SRAM, so a 400 MHz clock delivers back-to-back read or write bursts at full rate.
165-FBGA footprint — board-level reality
The supply rails need clean 1.8V and VDDQ decoupling per the QDR II layout guidelines; the 400 MHz edge rate punishes a sloppy ground via pattern. No AEC-Q100 qualification is listed, so this is an industrial/commercial part, not automotive.
Infineon lists the CY7C1565V18-400BZI as Obsolete. That means the factory last-time buy window has closed; new production is not coming. Sourcing now goes through independent distribution — broker channel, surplus stock, or customer inventory resale. Date codes will vary, and counterfeit screening (X-ray, decap, electrical test) is a standard gate before committing a production batch. The 165-FBGA package is not trivial to rework, so verify the die markings match Infineon's known-good devices.