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Join Date: Feb 2009
SDXC - 03-06-2009, 05:08 PM
News around the tech world is that Pretec has announced a 32GB SDXC card... higher capacity and faster transfer rates than SDHC. Here's my question... Anyone have any idea if these will work in our SD card readers in OSX? The "theoretical" size limit is 2 terabytes. I can only dream of having 2TB of space on my mini.
I did my own research this time and found that many people suspect that current SDHC card readers could receive a firmware update to allow the reader to see SDXC... the only issue that I've found is that the technology "relies heavily" on microsoft's exFAT format. Here's to hoping we something like this in the near future. Having the new 32GB card in my SD slot would be very appealing.
Dell Mini 9 - 64GB SSD - 2GB RAM
Join Date: Feb 2009
Location: Los Angeles
Re: SDXC - 03-08-2009, 09:47 PM
I think it's probably implementation-dependent. http://en.wikipedia.org/wiki/Secure_Digital_card#SDHC says that SDHC's on-card data structures can go up to 2TB, but SDHC cards are hard-coded to 32GB max.
SDHC cards have a 512 byte blocks and are block-addressed. The card's header lists the number of blocks the card has. 2TB / 512 bytes is 2^32 blocks, so the number of blocks is listed as a 32 bit integer. You only need 26 bits for 32GB, so SDHC cards hardwire the high 6 bits to zero. If the card reader ignores those 6 bits, it won't support more than 32GB SDXC cards. But it seems trivial to not ignore those bits, which means SDXC might work with no more than a firmware update. But I guess we'll have to wait and see if the Mini 9's reader can do that.
Now once we have 2TB SDXC cards, we'll have a problem -- we'll need a new, incompatible SD format to go any bigger. But that's probably not an issue for another few years.
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