The F429 uses both SDRAM and SRAM

[zyimi]

Whether the two buses can be used at the same time？ Winbond's SDRAM is used to find a high probability of reading and writing errors in SDRAM data。 but there is no problem with using ISSI. If you don't read or write to the external SRAM, it's fine。

[TDK]

Yes, SRAM and SDRAM can be used at the same time. Try slowing the SDRAM clock rate down by a factor of 10, could be a layout or noise issue.