Secure Digital card
The XO laptop has 1 MMC/SD/SDHC slot. 8-gigabyte memory cards work. As larger cards are created, they will also be tested (-gnu).
XO uses a custom microchip for SD card access, Camera and Flash Enabler, or CaFE. CaFE includes SDHC support. SDHC is compatible at a hardware level with SD. Pierre Ossman wrote the Linux driver support for SDHC. SD cards up to something like 256 GB should be supported. cafe is driven by the sdhci driver. cafe follows the standard host controller interface for SD controllers.
Here is how SD block addressing works: The address is 32 bits. In the CaFe chip, which is compatible with the standard "SDHCI" spec, the address goes in the 32-bit chip register at offset 8. For old SD cards (not the new SDHC - High Capacity cards), the address is a byte address, so the maximum size is 4 Gbytes. For the newer SDHC cards, the address is a block number, assuming 512 byte blocks, so the maximum size is 2 TBytes. None of this is CaFe-specific, BTW. It is standard SD.
Question: 16GB cards are starting to show up, I assume they *should* work, but has anyone tried one?
SD cards and USB flash drives are automatically mounted in the Journal activity. The Journal entry shows you how to access the add-on memory devices. You can move files to and from the storage media. Paul Bock 13:56, 19 December 2007 (EST)
Note: The SD/MMC/SDHC memory card will only mount when inserted properly into the XO laptop. The slot will allow you to insert the card in either direction however.
To properly insert the SD/MMC/SDHC card the brass fingers on the card should be facing up and towards the front of the LCD screen. Insert the card until it is flush with the bottom of the screen, you will hear a click when the card is fully seated.
The picture below shows the proper way to insert the SD/MMC/SDHC card:
--KenXo 11:28, 24 December 2007 (EST)
