7 ms·

Yes, but SDXC drivers don't necessarily support FAT32 on SDXC cards. The spec only requires exFAT. SDHC used FAT32.

userbinator 9y ago
That's interesting. It seems the SD specs (which include SDXC) are mandating a specific filesystem. According to https://en.wikipedia.org/wiki/Secure_Digital#SDXC https://en.wikipedia.org/wiki/Secure_Digital#SDXC Nevertheless, in order to be fully compliant with the SDXC card specification, many SDXC-capable host devices are firmware-programmed to expect exFAT on cards larger than 32 GB. Consequently, they may not accept SDXC cards reformatted as FAT32, even if the device supports FAT32 on smaller cards (for SDHC compatibility). That seems like a gross "abstraction layer violation" to me --- like making SATA controllers which work with SATA6 HDDs only when formatted with NTFS. The filesystem should have nothing to do with SD, which simply implements a block device abstraction. No doubt Microsoft was involved in this ridiculousness...
- deleted 9y ago
  [deleted]
- lathiat 9y ago
  since they receive patent licensing on exFAT, you can bet that! :) which is the same reason that there is no implementation in the kernel, only fuse. ugh.
- derefr 9y ago
  "SD" is basically the name of a standard stack, not a particular layer. You can reformat an SDHC card to not be FAT32, but then it won't be an SDHC card any more. There is a point to this: SD cards are used in all sorts of low-level embedded applications, with firmware that uses very inflexible (usually assembler) code to address the card. The assumptions about the SD wire protocol + the FAT32 filesystem + even the particular location of the FAT table on disk are all knotted together in these devices. Because of this, it's not even just that SDHC requires FAT32; SDHC requires FAT32 done with a specific formatting tool released by the SD standards group. Because your OS might put the FAT anywhere, but the tool puts it in exactly one place, and that's the place that dumb embedded devices expect to find it.

That's interesting. It seems the SD specs (which include SDXC) are mandating a specific filesystem. According to https://en.wikipedia.org/wiki/Secure_Digital#SDXC https://en.wikipedia.org/wiki/Secure_Digital#SDXC Nevertheless, in order to be fully compliant with the SDXC card specification, many SDXC-capable host devices are firmware-programmed to expect exFAT on cards larger than 32 GB. Consequently, they may not accept SDXC cards reformatted as FAT32, even if the device supports FAT32 on smaller cards (for SDHC compatibility). That seems like a gross "abstraction layer violation" to me --- like making SATA controllers which work with SATA6 HDDs only when formatted with NTFS. The filesystem should have nothing to do with SD, which simply implements a block device abstraction. No doubt Microsoft was involved in this ridiculousness...

deleted 9y ago
[deleted]
lathiat 9y ago
since they receive patent licensing on exFAT, you can bet that! :) which is the same reason that there is no implementation in the kernel, only fuse. ugh.
derefr 9y ago
"SD" is basically the name of a standard stack, not a particular layer. You can reformat an SDHC card to not be FAT32, but then it won't be an SDHC card any more. There is a point to this: SD cards are used in all sorts of low-level embedded applications, with firmware that uses very inflexible (usually assembler) code to address the card. The assumptions about the SD wire protocol + the FAT32 filesystem + even the particular location of the FAT table on disk are all knotted together in these devices. Because of this, it's not even just that SDHC requires FAT32; SDHC requires FAT32 done with a specific formatting tool released by the SD standards group. Because your OS might put the FAT anywhere, but the tool puts it in exactly one place, and that's the place that dumb embedded devices expect to find it.