This PSRAM is a 64 Mbit (8 Megabyte) serial pseudo SRAM device, organized in 8 M x 8 bits and in a compact SOIC-8 package. It is fabricated using the high-performance and high-reliability CMOS technology and can operates at 3.3V and can support up to 133 MHz clock rate. Note, however, that burst operations which cross page boundaries have a lower max input clock frequency at 84 MHz.
The PSRAM device can be accessed via basic Serial Peripheral Interface (SPI) or faster Quad Peripheral Interface (QPI) is supported if the application needs faster data rates. Because it is RAM not FLASH or EEPROM, this device supports unlimited reads and writes to the memory array.
A handy treat to upgrade an ESP32 based board or Teensy 4.1's that have a spot on the bottom for PSRAM addition. While it can be used with basic SPI or QSPI interfacing, its best used with chips that have memory-mapping support for external PSRAM so you get seamless operation.