MicroSD: New Card Issues

O.K. - I have seen the CRC problem with other cheap cards.

You can enable CRC with any card and it will increase reliability a great deal. Data is protected by a 16-bit CRC so SPI errors will be detected.

Performance for all cards will be reduced since calculating CRC requires CPU cycles. Run bench using a good card with and without CRC to see the hit.

I suspect that the performance of these new cards is very low. Edit bench.ino and decrease the file size to one MB by changing FILE_SIZE_MB like this:

#define FILE_SIZE_MB 1
#define FILE_SIZE (1000000UL*FILE_SIZE_MB)

bench.ino should run in 1/5 the time. Wait at least three minutes.