I have a question,when changed cpu from stmf407 to stm32f427 .sometimes, read a wrong data from extern sram access by FMC ,it's happend in most of the cases in interrupt ，someone have the same problem?

Can't this be a hardware problem, e.g. bad solder joint?

Is this still the same board, only with a different mcu?

And the system clock frequency did change or not?

JW

Have you tried more conservative (slower) FMC timing settings with the F427 variant ?

I found the cause of the problem. I used mode 1 before. When the chip selection was switched from norflsah to SRAM, there was an intermediate level in the bus. I don't know why the 407 chip didn't have this problem, but 427 did. Now I change to avoid reading data during this intermediate level

I don't quite understand the cause of your problem (appears to be both devices fighting for the bus, but why, once chipselects don't overlap?), but there are definitively differences in timing of FSMC in 'F40x and FMC in 'F42x, in what appears to be an identical setup https://community.st.com/s/question/0D50X0000C23GN6SQM/f427-fmc-vs-f407-fsmc-different-behaviour-for-backtoback-writes-to-the-same-sram-bank .

JW