External Flash (QSPI) vs Internal Flash Write Performance


I have some code written to copy PDM mic data into the external and then later dump it over UART. The issue I have is that when using the external flash, my audio gets corrupted because the QSPI flash writes don't keep up with the PDM data. However, when switching to the internal flash, I don't have this issue and the audio sounds clean. Now I thought the QSPI speed would dwarf the PDM speed, however, I'm not finding that to be the case. My question is, am I missing some sort of configuration register that's restricting it to low speed, or is this to be expected? Is there some limitation of the onboard flash on the dev kit?


PDM input: 50,000 int_16 samples per sec (3.2MHz)

QSPI CLK: 32MHz (measured on scope)