Differences between SDXC and SDHC standard? [closed]

Question

My cohorts and I at the Rockbox project have been reading with interest the announcement at the recent CES of the new SDXC standard for Secure Digital storage, but we have been left a little mystified as to the technical differences between the SDHC standard and the new SDXC one.

As we understand it, there are no technical limitations within SDHC that prevents card sizes of greater than 32 GB. The only limit is artificial (that is, it's written down in the standard). The technical limit of SDHC is the same as that announced as the official limit for SDXC which is 2 TB.

Is SDXC just an official ratification of SDHC beyond 32 GB, or is it actually a completely different implementation?

We're keen to make sure our SD drivers can read and write to these new cards, but details on the standard are hard to find at the moment (without signing an NDA with the SD organisation at any rate, and we're not about to do that).

Answer 1

From everything I've read (and no, I'm not privy to any NDA-covered info), it looks to be a incompatible on a HW-level.

Apparent Word of God says nothing else than "nya-nya, you need all new devices to use SDXC!". IMHO

Answer 2

Many devices list a maximum size of memory cards of 32 GB, based on the SDHC specifications, while some devices in practice do work with 64 GB SDXC cards, although they may have to be reformatted to FAT32 (used on SDHC) in stead of exFAT (used on SDXC, proprietary format). I base this on the Wikipedia article Secure Digital.

An example of devices that list as SDHC compatible but that accept 64 GB SDXC cards as well are certain Android smartphones.

The difference seems to be software based. An SDHC-compatible device may work with SDXC cards, if the device's OS can handle volumes larger than 32 GB, and it may be necessary to reformat the SDXC card to FAT32.