2014-01-15 02:48 AM
We checked some SDHC Card Readers and we noticed that they are using the Multiple Block Write CMD25 for writing a single sector and Multiple Block Read CMD18 for reading a sincle sector. The SDIO protocol has Single Block commands CMD24 and CMD 17 for writing or reading a single sector.
Does anyone know why the Card Readers are not using the single block commands for treating a single sector?
#sdio-cmd24-cmd172014-01-15 04:44 AM
The SD card specifications recommend to use ReadMultiBlocks and WriteMultiBlocks over ReadBlock and WriteBlock, I don't remember why specifically but based on my own experience with STM and SDIO is so much faster and efficient.
2014-01-15 05:26 AM
The command processing overhead is quite significant, streaming sequential reads/write are both far more efficient, and predictable (and thus optimized for and pipelined).
Practically all storage media works better with large collections of sectors handle at once, ie a whole cluster. Writing single blocks, or partial blocks, being by far the least efficient.2014-01-15 09:36 AM
Thanks, it make sense.