I tested the SD card write speed with the following setup:
HW: MPC574XG-MB + MPC574XG-176DS
SW: based on demo "sdhc_fatfs_mpc5748g"
I wrote a data buffer of 512 bytes into a new file, using f_write(), for 2000 times. And this took almost 3.5s. So roughly the write speed was 1MB / 3.5s = 290 KB/s. Is this a normal speed? Very slow, isn't it?