To activate SD-Card-support uncomment
//#define SDSUPPORT // Enable SD Card Support in Hardware Console
This is mandatory in 1.1 and it's RCs.
In older releases it may be enough to uncomment a dislay/pannel with a sd-card reader.
Uncommenting SDSUPPORT there does not harm.
--- Fix Me - On ---
The SD- or MMC- Card must be formatted as FAT and must have a MMC interface.
This is more likely with cards <= 2GB.
--- Fix Me - OFF ---