Hacker News new | ask | show | jobs
by ungzd 2354 days ago
Is there any real difference between SD, SDHC and SDXC, aside "SD uses FAT, SDHC uses FAT32, SDXC uses ExFat"? These cards does not have filesystem controller on it, it's not "FTP over wire", it's block-based storage device. If I format ancient SD from early 2000s with exFat, will it become SDXC?

From Wikipedia (marked with "Citation needed"):

> The SDHC format, announced in January 2006, brought improvements such as 32 GB storage capacity and mandatory support for FAT32 filesystems.

How dumb storage device can refuse to support FAT32?

Fun fact: SD cards support SPI interface and can be easily connected to cheap microcontrollers.
2 comments
duskwuff 2354 days ago
SD and SDHC differ in some material ways. SD uses byte-level addressing and is limited to a size of 2 GB. (The spec could theoretically support 4 GB, but is limited by spec to half that, possibly as a hedge against implementation errors.) SDHC uses sector-level addressing, lifting that limit to a theoretical 2 TB.

SDHC and SDXC are identical at a protocol level.

link
xenadu02 2354 days ago
In theory they support SPI. If you actually try to use it you'll find not only is it dog slow but half the cards out there aren't tested for it anymore and don't work at all or are very flaky.

I would not recommend using SPI mode.

link