The S25FL256SAGMFVR03: It speaks SPI with Quad I/O, hitting a 133 MHz clock rate that pushes read throughput well past what a standard SPI part can manage — useful when you are shadowing code to RAM or holding a FPGA configuration bitstream.
133 MHz and Quad I/O — what the clock speed buys you
At 133 MHz in Quad I/O mode, this part can deliver around 66 MB/s read throughput in Fast Read Quad Output mode. That matters if you are doing execute-in-place (XIP) from Flash or loading a large FPGA image at power-up — the bus is not the bottleneck. The Quad SPI interface is standard on modern MCUs and FPGAs, so the pin count stays at four data lines plus chip select and clock. No need for a parallel bus footprint.