MMC x SD CARD : Are these devices inter changeables ?

[andre_luis]

Hi,


I´m working on an embedded system in which I´m trying to fit an bootable linux IMG file, originally designed for a 2GB MMC, into a 2GB SD card with no success, due is lacking about 0,7% of all required clusters. I performed the same procedure by Win32DiskImager.exe, but returning exactly the same accounted result on missing clusters.

In order to understand what could be the reason, I suppose that perhaps I was originally using the wrong procedure to format those SD cards, which probably could irreversibly decrease its total avaliable space.

https://www.sdcard.org/downloads/formatter_4/

The SD Formatter was created specifically for memory cards using the SD/SDHC/SDXC standards. It is strongly recommended to use the SD Formatter instead of formatting utilities provided with operating systems that format various types of storage media. Using generic formatting utilities may result in less than optimal performance for your memory cards.

The SD/SDHC/SDXC memory cards have a "Protected Area" on the card for the SD standard's security function. The SD Formatter does not format the "Protected Area". Please use appropriate application software or SD-compatible device that provides SD security function to format the "Protected Area" in the memory card.

Does it make sense, or I really must use a 2GB-MMC instead actual 2GB-SD to fit this 2GB IMG file ? ( it is weird, due the system works properly with a higher SD card of 4GB ! )

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[FvM]

I don't expect that either the MMC or SDcard standards define what's excactly the capacity of a "2GB" card. At least it's not in the documents I have. But most likely the reserved "Protected Area" that isn't used in MMC is the reason why a 2GB chip gives less net C_SIZE in SDcards.