By default, FX3 master clock is set to 384MHz when using 19.2MHz crystal or clock source. "setSysClk400" field of CyU3PSysClockConfig_t structure should be set to CyTrue, when GPIF is operating in 32 bit mode at 100MHz.
The max frequency of operation of GPIF is 100MHz. When GPIF is configured in 32 bit mode and operating at 100MHz, the max data transfer rate that you can get theoretically is 400MBps.
Could you please provide the following info:
1.What is the GPIF data bus width and frequency at which GPIF is operating?
2.Are you connecting FX3 to a USB 2.0 port or USB 3.0 port?
Could you please use Cypress Streamer application to check the data throughput you are getting.