About the SD card slot
Summary
Some Mac computers feature an SD (Secure Digital) card slot that enables these computers to read and write data to SD media inserted in the slot. Learn more about the SD card slot.
Products Affected
MacBook Pro (13-inch, Mid 2009), MacBook Pro (15-inch, Mid 2009), MacBook Pro (15-inch, 2.53GHz, Mid 2009), iMac (21.5-inch, Late 2009), iMac (27-inch, Late 2009)
What is SD?
Secure Digital (SD) describes devices that conform to SD standards for non-volatile memory cards. See the SD Association website for more detailed information.
Are there size limitations for the cards that can be inserted into the SD slot?
Yes. The SD card specification for a memory card is 32 mm by 24 mm by 2.1 mm. You can also use thinner cards, such as MultiMediaCards (MMC). Cards that have a thickness greater than 2.1mm or that have surfaces that exceed 2.1mm, should not be used. Cards exceeding this size may damage the SD card slot if inserted and should not be used.
Which SD card formats work in the SD card slot?
Cards that conform to the SD 1.x and 2.x standards should work. The SD card slot can use cards that are Standard SD (Secure Digital) 4 MB to 4 GB and SDHC (Secure Digital High Capacity) 4 GB to 32 GB. MMC can also be used in this slot. MiniSD, MicroSD, and higher density formats like MiniSDHC and MicroSDHC can also work with the use of "passive" adapters that conform to the width and thickness specifications listed above.
Example of a passive adapter:
What is the maximum speed that my computer can use when reading and writing to an SD card in the SD card slot?
Your Macintosh has a maximum speed of 240 Mbit/s for SD media using the SD card slot. This exceeds the transfer rate of most SD media. Check the packaging that came with your SD media to determine the maximum transfer rate used by that media.
Does the SD slot work with cards that exceed 32 GB?
Yes. However, most media manufactures preformat the media using common block-and-cluster sizes that do not approach the theoretical limits of a given file system. Most SD cards use the FAT32 file format. Preformatted FAT32 SD media is commonly available up to a capacity of 32 GB. Some smaller capacity cards use the FAT16 file format. Preformatted FAT16 media is generally available up to a capacity of 2 GB.
Will the SD card slot work with SD cards that use the exFAT file system?
No.
How do I insert media into the SD card slot?
Insert a card with the metal contacts facing down and pointing toward the computer. Do not force media into the SD card slot. This may damage the SD card slot.
How does my Mac use the media inserted into the SD card slot?
Your computer recognizes a card inserted into the SD card slot as a USB storage device. The SD card can be mounted, read from, and written to just as any other USB storage device can.
I put the card in the slot, but it did not mount. What should I do?
Remove the card and insert it again. Sometimes, if you put the SD card into the slot too slowly, it may not mount properly.
When I try to write content to the card, I get a "cannot be modified" message. How can I fix this?
This message appears when you attempt to modify the contents of an SD card that is locked using the lock slider on the card. To edit data on the card, drag the icon representing the device to the Trash to eject the card. When the icon disappears from the desktop, remove the card from the computer. Adjust the slider tab to unlock the card, then reinsert the card into the slot. Refer to the manufacturers instructions for the location of the slider tab.
Can I reformat an SD card with Disk Utility?
Yes. Using Disk Utility, you can partition and format an SD device as FAT32 (using the MS-DOS FAT setting) or Mac OS Extended. The Mac OS Extended format can only be used on Macintosh systems. Cards formatted to Mac OS Extended will not be recognized by non-Apple systems.
Can I install Mac OS X on an SD storage device and use it as a startup volume?
Yes. Change the default partition table to GUID using Disk Utility, and format the card to use the Mac OS Extended file format to do so.
How do I remove a card from the SD card slot?
As with any USB storage device, allow any data transfer to SD media to complete before removing the card. When removing the card, the best way to insure the integrity of your data is to drag the icon that represents the card to the Trash, then remove the card from the slot after the icon disappears from your desktop.
Can I use SDIO (Secure Digital Input Output) cards?
No. Although SDIO cards are within the width and thickness specifications and should not damage the slot if inserted, they will not be recognized by the computer.
Can I use OS X to see the specifications for the interface hardware and media inserted in the SD card slot?
Yes. The System Profiler should provide information on the interface hardware and the media you inserted into the slot. To access the System Profiler, choose About This Mac from the Apple () menu. Click More Info, then select USB in the Hardware section. A list of USB devices should appear. Select Internal Memory Card Reader to access information about the interface hardware and the media inserted into the SD card slot.
Can I use the SD card slot while running Windows using Boot Camp?
Yes. The SD card slot works with Boot Camp in both Windows XP and Windows Vista.
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